To provide a switching device which can be applied to load demanding big electric current with suppressed arc short-circuit between contacts.

When commercial power source is used, a contact C1 is closed and a contact C2 is opened in a switching control section (61). With this arrangement, the electricity from commercial power source is supplied to a solenoid (632) of a first electromagnetic switch MG1 as the electricity is not supplied to a solenoid (642) of a second electromagnetic switch MG2 and its sub-contact (643) remains closed, which leads to a closure of a main contact (631) of the first electromagnetic switch MG1. On the other hand, a main contact (641) of the second electromagnetic switch MG2 is left opened as a contact C2 is opened {and the sub-contact (633) of the first electromagnetic switch is also opened}. When a generator is used, on the other way round, the contact C1 is opened and the contact C2 is closed in the switching control section (61).