A dovetailed building block includes a block body having a plurality of side surfaces. The side surfaces are constructed in an order of having a side surface with a dovetailed recess next to another surface with a dovetailed projection. The dovetailed projection of one said block body can engage the corresponding dovetailed recess of another said block body in a 90-degree cross manner. Thereupon, while in stacking a plurality of the block bodies, variety of secured and stable three-dimensional curved configuration can be built through angular engagement of one dovetailed projection of one block body and another dovetailed recess of another block body.