A machine tool comprising: a machining head including a rotation spindle and a spindle frame, the rotation spindle being disposed in the spindle frame; a friction stir welding tool (100, 200, 300, 400) mountable on the spindle frame; a machining table on which a workpiece is holdable; a tool storage which temporarily stores the friction stir welding tool (100, 200, 300, 400) therein; and an NC unit configured to control movement of the spindle frame and the machining table, wherein the friction stir welding tool (100, 200, 300, 400) comprises a pin holder (110, 210, 310, 410) comprising a shank connectable to the rotation spindle, a stir pin (140, 240, 340, 440) mountable on the pin holder (110, 210, 310, 410), and a housing (120, 220, 320, 420) comprising: a cylindrical portion (122, 222, 322, 422) through which the pin holder (110, 210, 310, 410) is passable; and a plate portion (124, 224, 324) connectable to the spindle frame, wherein a shoulder (152, 254, 354, 454a) is disposed at one end of the cylindrical portion (122, 222, 322, 422), wherein the tool storage comprises a tool magazine which stores a stock of the pin holders (110, 210, 310, 410) therein, and wherein an engaged portion (126, 226, 326) engageable with the spindle frame is fixed to an upper surface of the plate portion (124, 224, 324), characterized in that the tool storage further comprises a housing storage table which is separate from the tool magazine and which is disposed within the movable range of the machining head. a machining head including a rotation spindle and a spindle frame, the rotation spindle being disposed in the spindle frame; a friction stir welding tool (100, 200, 300, 400) mountable on the spindle frame; a machining table on which a workpiece is holdable; a tool storage which temporarily stores the friction stir welding tool (100, 200, 300, 400) therein; and an NC unit configured to control movement of the spindle frame and the machining table, wherein the friction stir welding tool (100, 200, 300, 400) comprises a pin holder (110, 210, 310, 410) comprising a shank connectable to the rotation spindle, a stir pin (140, 240, 340, 440) mountable on the pin holder (110, 210, 310, 410), and a housing (120, 220, 320, 420) comprising: a cylindrical portion (122, 222, 322, 422) through which the pin holder (110, 210, 310, 410) is passable; and a plate portion (124, 224, 324) connectable to the spindle frame, a pin holder (110, 210, 310, 410) comprising a shank connectable to the rotation spindle, a stir pin (140, 240, 340, 440) mountable on the pin holder (110, 210, 310, 410), and a housing (120, 220, 320, 420) comprising: a cylindrical portion (122, 222, 322, 422) through which the pin holder (110, 210, 310, 410) is passable; and a plate portion (124, 224, 324) connectable to the spindle frame, a cylindrical portion (122, 222, 322, 422) through which the pin holder (110, 210, 310, 410) is passable; and a plate portion (124, 224, 324) connectable to the spindle frame, wherein a shoulder (152, 254, 354, 454a) is disposed at one end of the cylindrical portion (122, 222, 322, 422), wherein the tool storage comprises a tool magazine which stores a stock of the pin holders (110, 210, 310, 410) therein, and wherein an engaged portion (126, 226, 326) engageable with the spindle frame is fixed to an upper surface of the plate portion (124, 224, 324), characterized in that the tool storage further comprises a housing storage table which is separate from the tool magazine and which is disposed within the movable range of the machining head.