An assembling apparatus comprising: a shaft member having a linear assembling function and a rotational assembling function; and a base configured to support the shaft member so that the shaft member is movable in an axial direction and axially rotatable; and a drive unit (4, 8) which can move the shaft member in the axial direction and axially rotate the shaft member, wherein the drive unit (4, 8) comprises a motor and a power conversion mechanism switchably converting output of the motor to axial movement and axial rotation of the shaft member, wherein the power conversion mechanism comprises: a linear motion mechanism which is connected to the motor, the linear motion mechanism capable of moving the shaft member in the axial direction with respect to the base using the output of the motor, a rotation mechanism which axially rotates the shaft member with respect to the base, and a switching mechanism which connects and disconnects the motor and the rotation mechanism, wherein the linear motion mechanism comprises a first member in which the shaft member is inserted, the first member is attached to the base such that it is axially rotatable, a first engagement portion is formed on the first member, the first engagement portion slidably engages a male screw formed on the shaft member, the male screw extends in a spiral manner, the rotation mechanism comprises a second member in which the shaft member is inserted, the second member is attached to the base such that it is axially rotatable, a second engagement portion is formed at the second member, the second engagement portion slidably engages a spline formed on the shaft member, and the spline extends in the axial direction, characterized in that the switching mechanism comprises a clutch for connecting or disconnecting the first member and the second member, the clutch has a clutch base and a clutch body, the shaft member is inserted into the clutch body, the clutch body is moveable in the axial direction, a stopper member is provided on the outer peripheral surface of the clutch body, the stopper member being engageable with an engagement portion (2d1) of the base in a first state to prevent the axial rotation of the clutch with respect to the second member around the shaft member wherein the shaft member is moveable in the axial direction, and the stopper member being shiftable with respect to the engagement portion (2d1) in a second state to allow axial rotation of the clutch with the shaft member. a shaft member having a linear assembling function and a rotational assembling function; and a base configured to support the shaft member so that the shaft member is movable in an axial direction and axially rotatable; and a drive unit (4, 8) which can move the shaft member in the axial direction and axially rotate the shaft member, wherein the drive unit (4, 8) comprises a motor and a power conversion mechanism switchably converting output of the motor to axial movement and axial rotation of the shaft member, wherein the power conversion mechanism comprises: a linear motion mechanism which is connected to the motor, the linear motion mechanism capable of moving the shaft member in the axial direction with respect to the base using the output of the motor, a rotation mechanism which axially rotates the shaft member with respect to the base, and a switching mechanism which connects and disconnects the motor and the rotation mechanism, a linear motion mechanism which is connected to the motor, the linear motion mechanism capable of moving the shaft member in the axial direction with respect to the base using the output of the motor, a rotation mechanism which axially rotates the shaft member with respect to the base, and a switching mechanism which connects and disconnects the motor and the rotation mechanism, wherein the linear motion mechanism comprises a first member in which the shaft member is inserted, the first member is attached to the base such that it is axially rotatable, a first engagement portion is formed on the first member, the first engagement portion slidably engages a male screw formed on the shaft member, the male screw extends in a spiral manner, the rotation mechanism comprises a second member in which the shaft member is inserted, the second member is attached to the base such that it is axially rotatable, a second engagement portion is formed at the second member, the second engagement portion slidably engages a spline formed on the shaft member, and the spline extends in the axial direction, the switching mechanism comprises a clutch for connecting or disconnecting the first member and the second member, the clutch has a clutch base and a clutch body, the shaft member is inserted into the clutch body, the clutch body is moveable in the axial direction, a stopper member is provided on the outer peripheral surface of the clutch body, the stopper member being engageable with an engagement portion (2d1) of the base in a first state to prevent the axial rotation of the clutch with respect to the second member around the shaft member wherein the shaft member is moveable in the axial direction, and the stopper member being shiftable with respect to the engagement portion (2d1) in a second state to allow axial rotation of the clutch with the shaft member.