A motor drive device assembly capable of suppressing differences in temperatures of motor drive devices depending on operational conditions. The motor drive device assembly includes a first motor drive device including a first heatsink, a second motor drive device located adjacent to the first motor drive device and including a second heatsink formed separately from the first heatsink, and a connection part connecting the first heatsink and the second heatsink to each other, to allow thermal conduction between the first heatsink and the second heatsink.