A C-type welding gun capable of accurately operating irrespective of the posture of the C-type welding gun without forcibly pressing electrodes to a workpiece and without considering thickness of the workpiece, wear of electrodes, etc. The C-type welding gun includes two servomotors attached to a housing, a C-shaped arm fixed to the housing and a movable arm provided in the housing. A mechanism for converting the rotation of the output shaft of one servomotor into the reciprocal motion of the movable arm is housed in the housing. A mechanism for converting the rotation of the output shaft of the other servomotor into the reciprocal motion of the C-shaped arm is provided between the wrist of the robot and the housing. Both the servomotors are simultaneously actuated while the other servomotor is stopped in response to the signal representing the contact of the electrode of the C-shaped arm to the workpiece.