A transmission mount type of side assembling includes a cylindrical insulator; a core having a plurality of longitudinal holes and inserted in the insulator; a side stopper having a support connected to one end of the core in contact with the inner side of the insulator and a protrusion protruding outside the insulator from the support; a cylindrical case accommodating the core, the side stopper, and the insulator; and a plurality of bolts that is longer than the case and inserted through holes in the core and the side stopper from a side to protrude outside the case, such that it can simplify the assembly process of fastening a transmission to a car body and reduce the manufacturing cost, without changing the existing manufacturing line, and ensure safety in assembly.