A hole-drilling device for drilling a hole with an expanded diameter hole portion, the hole-drilling device comprising: a body including a shank at its rear part; a sleeve attached to a front part of the body such that the sleeve is movable relative to the body in a front-rear direction over a predetermined range, the sleeve including a contacting portion at its front end, the contacting portion coming into contact with a surface of a drilling object; a drill bit body provided with a drilling bit at its distal end, the drill bit body being configured such that a proximal end portion of the drill bit body is inserted in a bottomed insertion hole formed in the front part of the body, the drill bit body being inserted in and attached to the sleeve such that the drill bit body is movable in the front-rear direction; an expanded diameter hole portion forming member provided with a cutting bit at its distal end and attached to a side surface of the drill bit body such that the expanded diameter hole portion forming member is movable in the front-rear direction, the cutting bit protruding laterally from the drill bit body when the expanded diameter hole portion forming member moves forward on the side surface of the drill bit body; a cam rotatably supported by the body and provided with contacting portions at both sides with respect to a rotation center, one of the contacting portions being contacted by a predetermined portion of an inner wall of the sleeve, the other contacting portion being contacted by a proximal end portion of the expanded diameter hole portion forming member, wherein the expanded diameter hole portion forming member is configured to move forward on the side surface of the drill bit body owing to rotation of the cam when the body moves forward relative to the sleeve; a first urging unit that urges the sleeve forward relative to the body and a second urging unit that urges the expanded diameter hole portion forming member rearward relative to the drill bit body; wherein a rear end surface is provided at the sleeve and a sleeve contact surface which contacts with the rear end surface is provided at the body; and the range of movement of the sleeve relative to the body is restricted to a range from a state where the body is urged rearwardly relative to the sleeve by the first urging unit to a state where the sleeve contact surface of the body is in contact with the rear end surface of the sleeve. a body including a shank at its rear part; a sleeve attached to a front part of the body such that the sleeve is movable relative to the body in a front-rear direction over a predetermined range, the sleeve including a contacting portion at its front end, the contacting portion coming into contact with a surface of a drilling object; a drill bit body provided with a drilling bit at its distal end, the drill bit body being configured such that a proximal end portion of the drill bit body is inserted in a bottomed insertion hole formed in the front part of the body, the drill bit body being inserted in and attached to the sleeve such that the drill bit body is movable in the front-rear direction; an expanded diameter hole portion forming member provided with a cutting bit at its distal end and attached to a side surface of the drill bit body such that the expanded diameter hole portion forming member is movable in the front-rear direction, the cutting bit protruding laterally from the drill bit body when the expanded diameter hole portion forming member moves forward on the side surface of the drill bit body; a cam rotatably supported by the body and provided with contacting portions at both sides with respect to a rotation center, one of the contacting portions being contacted by a predetermined portion of an inner wall of the sleeve, the other contacting portion being contacted by a proximal end portion of the expanded diameter hole portion forming member, wherein the expanded diameter hole portion forming member is configured to move forward on the side surface of the drill bit body owing to rotation of the cam when the body moves forward relative to the sleeve;