A ribbon cassette comprising: a box like case; an ink ribbon accommodated in an interior of the case; a first spool having hollow cylindrical shape and rotatably supported in the case, one end portion of the ink ribbon being wound over the first spool; a second spool having hollow cylindrical shape and rotatably supported in the case, another end portion of the ink ribbon being connected to the second spool; a rotating member disposed in an interior of the first spool and engaged with a first inner surface which is a part of an inner surface of the first spool; a clutch spring comprising a coil like annular part attached to the rotating member, and an extension part extending from the annular part; and an engaging part provided in the case and positioned on a locus of rotation of the extension part, wherein the first spool has a specific protruding portion provided at a second inner surface which is another part of the inner surface of the first spool and is positioned at a different position from a position of the first inner surface with respect to a first direction which is an extending direction of a rotation axis of the first spool, the specific protruding portion protruding in a second direction crossing the rotation axis of the first spool; and characterized in that the case has a case-hole positioned closer to the second inner surface than to the first inner surface, the case-hole having a portion overlapped in the first direction with an entire circular region surrounded by a path of rotation of a tip end portion in the second direction of the specific protruding portion, the case-hole being in communication with the interior of the first spool. a box like case; an ink ribbon accommodated in an interior of the case; a first spool having hollow cylindrical shape and rotatably supported in the case, one end portion of the ink ribbon being wound over the first spool; a second spool having hollow cylindrical shape and rotatably supported in the case, another end portion of the ink ribbon being connected to the second spool; a rotating member disposed in an interior of the first spool and engaged with a first inner surface which is a part of an inner surface of the first spool; a clutch spring comprising a coil like annular part attached to the rotating member, and an extension part extending from the annular part; and an engaging part provided in the case and positioned on a locus of rotation of the extension part, wherein the first spool has a specific protruding portion provided at a second inner surface which is another part of the inner surface of the first spool and is positioned at a different position from a position of the first inner surface with respect to a first direction which is an extending direction of a rotation axis of the first spool, the specific protruding portion protruding in a second direction crossing the rotation axis of the first spool; and characterized in that the case has a case-hole positioned closer to the second inner surface than to the first inner surface, the case-hole having a portion overlapped in the first direction with an entire circular region surrounded by a path of rotation of a tip end portion in the second direction of the specific protruding portion, the case-hole being in communication with the interior of the first spool.