A webbing take-up device comprising: a device main body comprising a spool, the spool taking up a webbing from a base end side thereof in a webbing length direction onto an outer peripheral portion of the spool by rotating in a take-up direction that is one direction about a center axis of the spool; an acceleration detection section that is provided at the device main body so as to be capable of rotating with respect to the device main body about an axis whose axial direction is a specific direction such that, accompanying tilting of the device main body, the acceleration detection section maintains the same orientation as orientation of the acceleration detection section in a state prior to the device main body tilting, a placement face, formed in a concave shape that is open upwards, being formed at the acceleration detection section, a spherical shaped inertia mass body being placed on the placement face, the inertia mass body rolling on the placement face due to inertia at a time of a sudden vehicle deceleration, the placement face being configured to include a general face and a restriction face (100, 102), the general face being a shape that an inner peripheral profile is open upwards, the restriction face (100, 102) being formed on at least one side further than a center of the placement face in a vehicle left-right direction as seen in plan view from an open direction side of the placement face; and a lock section that is actuated by the spool rotating in a pull-out direction that is the opposite direction from the take-up direction in a state in which the inertia mass body of the acceleration detection section rolls on the placement face, rotation of the spool in the pull-out direction being restricted by actuation of the lock section; characterized in that an angle of incline (θ2), with respect to a horizontal direction, of the restriction face (100, 102) in a cross-section of the placement face taken along the axial direction of the acceleration detection section, being larger than an angle of incline (θ1), with respect to the horizontal direction, of the general face in a cross-section of the placement face taken along a direction orthogonal to the axial direction, such that rolling of the inertia mass body on the placement face in the vehicle left-right direction is restricted to a greater extent than rolling of the inertia mass body on the placement face in a vehicle front-rear direction. a device main body comprising a spool, the spool taking up a webbing from a base end side thereof in a webbing length direction onto an outer peripheral portion of the spool by rotating in a take-up direction that is one direction about a center axis of the spool; an acceleration detection section that is provided at the device main body so as to be capable of rotating with respect to the device main body about an axis whose axial direction is a specific direction such that, accompanying tilting of the device main body, the acceleration detection section maintains the same orientation as orientation of the acceleration detection section in a state prior to the device main body tilting, a placement face, formed in a concave shape that is open upwards, being formed at the acceleration detection section, a spherical shaped inertia mass body being placed on the placement face, the inertia mass body rolling on the placement face due to inertia at a time of a sudden vehicle deceleration, the placement face being configured to include a general face and a restriction face (100, 102), the general face being a shape that an inner peripheral profile is open upwards, the restriction face (100, 102) being formed on at least one side further than a center of the placement face in a vehicle left-right direction as seen in plan view from an open direction side of the placement face; and a lock section that is actuated by the spool rotating in a pull-out direction that is the opposite direction from the take-up direction in a state in which the inertia mass body of the acceleration detection section rolls on the placement face, rotation of the spool in the pull-out direction being restricted by actuation of the lock section; characterized in that an angle of incline (θ2), with respect to a horizontal direction, of the restriction face (100, 102) in a cross-section of the placement face taken along the axial direction of the acceleration detection section, being larger than an angle of incline (θ1), with respect to the horizontal direction, of the general face in a cross-section of the placement face taken along a direction orthogonal to the axial direction, such that rolling of the inertia mass body on the placement face in the vehicle left-right direction is restricted to a greater extent than rolling of the inertia mass body on the placement face in a vehicle front-rear direction.