A power-circuit breaking device, which can easily mount a fuse and has a small number of component and a simple structure. The power-circuit breaking device includes a first connector housing having a pair of circuit terminals connected with a power circuit, and a second connector housing closing the power circuit by fitting with the first connector housing. The second connector housing includes a fuse having a pair of terminals to be connected with the pair of circuit terminals, a housing having a lock arm engaged with a cutout provided at the terminal and a cover an entry opening of a receiving section of the housing. The cover includes a limiter limiting the lock arm to move to disengaging the terminal.