A sensor insertion device includes a first elastic member； a second elastic member； an elastic energy variable mechanism configured to elastically deform the first elastic member and the second elastic member to achieve an energy accumulated state； a first holding mechanism configured to hold a position of the first elastic member in the energy accumulated state； and a second holding mechanism configured to hold a position of the second elastic member in the energy accumulated state for a period of time during which, after the release of the first elastic member from the first holding mechanism in the energy accumulated state, the needle member is moved to the insertion position by the first elastic energy.
