A printing device, comprising: a main body having a head support surface on which a thermal head is supported; and a cassette including a plate-shaped cassette base, a supply roll shaft, and a winding roll shaft, and detachably attached to the head support surface of the main body along an axis direction of the supply roll shaft and the winding roll shaft, the supply roll shaft rotatably supporting a ribbon supply roll and being provided on one side, in a predetermined direction, of a facing surface of the cassette base facing the head support surface, and the winding roll shaft rotatably supporting a ribbon winding roll and being provided on an other side, in the predetermined direction, of the facing surface, wherein the printing device is configured to perform printing by transferring ink of an ink ribbon onto a print medium due to heating of the thermal head, the ink ribbon being fed out from the ribbon supply roll and wound around the ribbon winding roll through the thermal head, and wherein the printing device further comprises: a guided portion (50, 500) provided on the facing surface of the cassette base; and a guide portion (38, 138) provided at a position facing the guided portion on the head support surface of the main body, and configured to guide and locate the guided portion to a predetermined position on a side of the head support surface along the axis direction, characterized in that the printing device further comprises: a lock unit provided in the guided portion and configured to lock the guided portion to the guide portion in a state where the guided portion is located at the predetermined position by the guide portion; and a release unit configured to release locking performed by the lock unit. a main body having a head support surface on which a thermal head is supported; and a cassette including a plate-shaped cassette base, a supply roll shaft, and a winding roll shaft, and detachably attached to the head support surface of the main body along an axis direction of the supply roll shaft and the winding roll shaft, the supply roll shaft rotatably supporting a ribbon supply roll and being provided on one side, in a predetermined direction, of a facing surface of the cassette base facing the head support surface, and the winding roll shaft rotatably supporting a ribbon winding roll and being provided on an other side, in the predetermined direction, of the facing surface, wherein the printing device is configured to perform printing by transferring ink of an ink ribbon onto a print medium due to heating of the thermal head, the ink ribbon being fed out from the ribbon supply roll and wound around the ribbon winding roll through the thermal head, and wherein the printing device further comprises: a guided portion (50, 500) provided on the facing surface of the cassette base; and a guide portion (38, 138) provided at a position facing the guided portion on the head support surface of the main body, and configured to guide and locate the guided portion to a predetermined position on a side of the head support surface along the axis direction, a guided portion (50, 500) provided on the facing surface of the cassette base; and a guide portion (38, 138) provided at a position facing the guided portion on the head support surface of the main body, and configured to guide and locate the guided portion to a predetermined position on a side of the head support surface along the axis direction, characterized in that the printing device further comprises: a lock unit provided in the guided portion and configured to lock the guided portion to the guide portion in a state where the guided portion is located at the predetermined position by the guide portion; and a release unit configured to release locking performed by the lock unit. a lock unit provided in the guided portion and configured to lock the guided portion to the guide portion in a state where the guided portion is located at the predetermined position by the guide portion; and a release unit configured to release locking performed by the lock unit.