Toy building block

1. A toy building block that can create a cubic article by assembling a unit piece, said unit piece comprising:

a plate body made of a flexible material in which an outer profile of the plate body is formed by a pair of upper and lower short sides curved inward and a pair of right and left long sides curved inward;

projections provided at a corner portions located on one of diagonal lines of said plate body on a plate face of the plate body at a right angle; and

through holes into which said projections can be fitted, the through holes being provided at the corner portions located on the other diagonal line of the plate body.

2. The toy building block according to claim 1 , wherein:

said plate body is formed in a frame shape in which a gourd-shaped opening substantially following said outer profile is opened on an inner side of the plate body.

3. The toy building block according to claim 1 , wherein:

said corner portion is formed to have a substantially circular outer profile.

4. The toy building block according to claim 1 , wherein:

said projection has a length such that a head portion is exposed from said through hole, and the head portion is extended outward in a radial direction.

5. The toy building block according to claim 1 , wherein:

a plurality of the unit pieces classified into a plurality of piece groups, each of the piece group having its own color that is different from the other piece group.