A seat lock apparatus includes: a hook member configured to be rotationally biased elastically in a positive direction; an interlocking unit configured to restrict rotation of the hook member in a negative direction; and a cover member configured to cover an operation range of the hook member at one side of the hook member, the cover member including a striker entrance groove that a striker enters. The hook member includes an engagement groove. The engagement groove has both end portions at a side of an opening of the engagement groove, each end portion being beyond the striker entrance groove to overlap the cover member as viewed along a shaft direction of the hook member when the hook member is at a position of being restricted from operating by the interlocking unit.