A stackable breadboard includes a plurality of through holes formed therein, including a plurality of first insertion holes that extends through a top surface a bottom surface thereof and a plurality of second insertion holes that extend through the top surface and side surfaces thereof. The first insertion holes extends longitudinally to allow more than one breadboard to connect in a longitudinally stacked arrangement through male and female connection terminals thereby achieving a three-dimensional stacked arrangement that effectively reduce the surface area occupied thereby. Further, the second insertion holes are arranged to extend, at opposite ends thereof, in the longitudinal and transverse directions to allow more than one breadboard to connect to each other sideways by means of the male and female connection terminals to achieve expansion of the functionality thereof.