A cooler reduces size increase. The cooler includes a main container including a refrigeration compartment, and a battery mount set including a first battery mount to which a first battery is attachable and a second battery mount to which a second battery different from the first battery is attachable. The first battery mount and the second battery mount are positioned relative to each other to cause the second battery to be unattachable to the second battery mount when the first battery is attached to the first battery mount and to cause the first battery to be unattachable to the first battery mount when the second battery is attached to the second battery mount.