The heatsensitive stencil sheet perforating device of this invention comprises a pedestal (1) for an original being mounted thereon; a pressing body (2) attached pivotaly on one end of the pedestal (1) for supporting a heatsensitive stencil sheet on an area corresponding to the original mounted on the pedestal (1); a light irradiation device (3) attached detachably to the pressing body (2) in a defined state, including a light source (13) for irradiating the heatsensitive stencil sheet; a power supply device (15) installed inside of the pressing body (2), for supplying electric energy to emit light from the light source (13); a first contact member (14) attached to the light irradiation device (3), connected to the light source (13); a second contact member (18) attached to the pressing member (2), connected to the power source (16) of the power supply device (15), so as to come into contact with the first contact member (14) when the light irradiation device (3) is engaged in the pressing body (2) in a defined state; and a support member (20) attached to the pressing body (2), for supporting the light irradiation device (3) by receiving a part of the light irradiation device (3) not to bring the first contact member (14) into contact with the second contact member (19), when the light irradiation device (3) is attached to the pressing body (2) not in the defined state.