To provide a controller that enables a control part such as a microcomputer to be shared by a variety of refrigerating devices, while also making it possible to set the number of relays at a necessary number.

The controller has a control board 12 with a control part 11, and a relay board 14 with a plurality of relays 13 that are controlled by the control part 11. Since the control board 12 and the relay board 14 are thus separated from each other, the control part 11 can be shared by a variety of refrigerating devices regardless of the number of relays 13 and the control part 11 can be made versatile.