A medicinal-liquid administering device (10) includes a reusable part (14) and a disposable part (12) that is attachable to the reusable part (14). A cover part (92) is provided at an opening part (100) of a housing (90), which houses a reusable-side power transmission part (88) that is engageable with a disposable-side power transmission part (24). At the time of attaching the disposable part (12) to the reusable part (14), the cover part (92) contacts a contact part (132) of the disposable part (12) to be opened and maintain the opened state while resisting pushing force of a pushing member (94). When the disposable part (12) is detached from the reusable part (14), the cover part (92) is closed to block the opening part (100) of the housing (90) by the pushing force of the pushing member (94).
