Adjustable neck brace

1. An adjustable neck brace, including:

a neck collar, including only one sliding engaging groove which is disposed at middle front of the neck collar, the only one sliding engaging groove extending in a first extension direction and having a first engaging portion;

only one positioning member, attached to the neck collar and movable along the only one sliding engaging groove, having a second engaging portion, the second engaging portion being releasably positioningly engaged with the first engaging portion;

a chin support, relatively movably connected to the neck collar;

at least one connecting member, connecting the only one positioning member and the chin support;

wherein the positioning member includes a mount portion which is slidably arranged on the neck collar and an operating member which is connected to the mount portion, the at least one connecting member is connected to the mount portion, and the operating portion has the second engaging portion;

wherein the neck collar further includes two through slots extending in a second extension direction and located by two sides of the only one sliding engaging groove, the mount portion includes two wing portions, a distal end of each said wing portion is disposed through one of the through slots, and the distal end of each said wing portion is connected to one of the connecting members wherein the first extension direction is different than the second extension direction and wherein the mount portion includes a base having the two wing portions and two blocking walls connected to two sides of the base, the operating member is disposed between the two blocking walls, an elastic member is disposed between the operating member and the base, and the elastic member makes the second engaging portion have a tendency to move toward the first engaging portion normally.

2. The adjustable neck brace of claim 1 , wherein the two blocking walls are detachably connected to the base.

3. The adjustable neck brace of claim 2 , wherein the first engaging portion includes a plurality of recesses arranged along the extension direction in intervals, each said recess has two sides each having a spacing wall, and the second engaging portion includes an engaging block which is releasably positioningly engaged with one of the recesses; the neck collar further has two guiding slots, the two guiding slots are located by the two sides of the only one sliding engaging groove and extend tiltedly away from the only one sliding engaging groove, a number of the at least one connecting member is two, one of the two end portions of each said connecting member is slidably disposed within one of the guiding slots, and the other of the two end portions of each said connecting member is pivoted to one of the wing portions; the neck collar has an inner wall which is curved, and the two connecting members are flexible and extend along the inner wall of the neck collar; the two blocking walls are opposite to the two spacing walls of one of the recesses and capable of positioningly restricting the operating member therebetween.