An electric power tool in which a motor located in a housing is a built-in motor that does not have a motor case, the electric power tool comprising: a first retainer (40, 41) that is provided on an inner circumferential surface of the housing and retains an outer circumference of the motor; a transmission mechanism that transmits a rotational output of the motor to a front-end tool; and a rotation detector that detects an angle of rotation of the motor, wherein the rotation detector includes a rotating body attached to a motor shaft of the motor and a position detector that outputs a rotational position signal corresponding to a rotational position of the rotating body, characterized by the electric power tool further comprising: a second retainer that is provided on the inner circumferential surface of the housing and retains the position detector at a position facing the rotating body in a direction of rotational axis, further comprising: a third retainer that is provided on the inner circumferential surface of the housing and retains an outer circumference of a bearing that supports the motor shaft; a linking rib that links the second retainer and the third retainer, wherein the linking rib is provided on the inner circumferential surface of the housing to extend in a direction of rotational axis. a first retainer (40, 41) that is provided on an inner circumferential surface of the housing and retains an outer circumference of the motor; a transmission mechanism that transmits a rotational output of the motor to a front-end tool; and a rotation detector that detects an angle of rotation of the motor, wherein the rotation detector includes a rotating body attached to a motor shaft of the motor and a position detector that outputs a rotational position signal corresponding to a rotational position of the rotating body, characterized by the electric power tool further comprising: a second retainer that is provided on the inner circumferential surface of the housing and retains the position detector at a position facing the rotating body in a direction of rotational axis, further comprising: a third retainer that is provided on the inner circumferential surface of the housing and retains an outer circumference of a bearing that supports the motor shaft; a linking rib that links the second retainer and the third retainer, wherein the linking rib is provided on the inner circumferential surface of the housing to extend in a direction of rotational axis. a second retainer that is provided on the inner circumferential surface of the housing and retains the position detector at a position facing the rotating body in a direction of rotational axis, further comprising: a third retainer that is provided on the inner circumferential surface of the housing and retains an outer circumference of a bearing that supports the motor shaft; a linking rib that links the second retainer and the third retainer, wherein the linking rib is provided on the inner circumferential surface of the housing to extend in a direction of rotational axis. a third retainer that is provided on the inner circumferential surface of the housing and retains an outer circumference of a bearing that supports the motor shaft; a linking rib that links the second retainer and the third retainer, wherein the linking rib is provided on the inner circumferential surface of the housing to extend in a direction of rotational axis.