A substrate unit includes a first connector including a first terminal and a first housing accommodating the first terminal, and to be connected to an external connector, a first substrate on which the first connector is mounted, a second connector including a second terminal and a second housing accommodating the second terminal, and to be connected to the external connector, a second substrate on which the second connector is mounted and a case accommodating the first substrate and the second substrate. The first housing is provided with a first locking portion. The second housing is provided with a second locking portion. The first locking portion and the second locking portion are locked to each other. The first terminal and the second terminal are disposed to face an opening provided in the case through which the external connector is to be connected to the first connector and the second connector.