The invention provides a chain block and a built-in cover with which it is possible to relatively easily prevent a lubricant from running out even if the gear ratio or gear configuration changes. A chain block (10) has: a gear unit (30) that is equipped with a pinion gear (31) and a load gear (34), which is coaxial with the pinion gear (31) and can rotate relatively thereto; case bodies (41, 70) that store a gear unit and are supplied with grease; and a built-in cover (100) that is disposed inside the case bodies (41, 70) so as to be separate therefrom. The built-in cover (100) is equipped with a first peripheral wall part (110) that covers the outer peripheral side of the pinion gear (31), and a second peripheral wall part (120) that covers the periphery of a first driven gear body (32) including a first large-diameter driven gear (32a), which has a larger diameter than the pinion gear (31). Because the first peripheral wall part (110) and the second peripheral wall part (120) are continuous, the built-in cover (100) is formed in an uninterrupted circumferential shape.