To cultivate imagination by forming a building block by a fitting part on which a design is printed or fitted and a rectangular parallelopiped shaped frame body having a through hole of a shape compensating with this fitting part at the center, bisecting this building block in a thickness direction and manufacturing each of the building blocks into thin plate ones by injection molding.

A design in which a lion is drawn like a comic picture, for instance, is printed on the surface of a building block and the building block is divided into a fitting part fitted in the shape of the design and a rectangular parallelopiped shaped frame body having a through hole 5 opened in a shape compensating with the fitting part at the center part. The fitting part and the frame body are completed by coupling two parts divided into surface sides 1a, 2a and rear sides 1b, 2b at the center of each thickness direction and a surface on which a through hole 5 of the frame bodies 2a, 2b is formed is formed into a square shape. Each parts of these fitting part, surface sides 1a, 2a and rear sides 1b, 2b of the frame bodies is formed by performing injection molding for each PVC(polyvinyl chloride) and subsequently, the surface sides 1a, 2a and the rear sides 1b, 2b are coupled.