A lock mechanism with a tubular body comprising: a housing having one end to which the tubular body provided with an engagement portion is at least mounted; a lock member formed of a metallic wire rod having elasticity, that is configured to lock and unlock the housing and the tubular body; a ring member that is rotatably attached on an outer periphery of the housing and is configured to move the lock member between a lock position and an unlock position, characterized in that the ring member includes a locking portion cut and raised as an elastic element from an annular wall, said locking portion comprising an engagement projection, and in that the housing comprises a locked portion formed as a hole portion, such that when the locking portion is locked to the locked portion, the lock member is retained in the unlock position in a state where an urging force is accumulated in the lock member; when the tubular body is inserted in the housing to unlock the locking portion and release the urging force accumulated in the lock member, the engagement projection of the ring member is pushed out of the locked portion, the lock member moves to the lock position together with the ring member to lock the tubular body; and when the ring member is slid in an axis direction of the tubular body after being locked, a fitting portion provided in the ring member is fitted in a fitted portion provided in the housing to prevent rotation of the ring member, wherein, in order to release the engagement between the tubular body and the housing, first, the fitting portion is separated from the fitted portion by sliding the ring member axially, next, the ring member is rotated in an unlock direction, which causes one tip portion of the lock member to slide on a slide inclined surface included in the housing, whereby the lock member is enlarged to open in an outer peripheral direction in order to arrive to the unlock position. a housing having one end to which the tubular body provided with an engagement portion is at least mounted; a lock member formed of a metallic wire rod having elasticity, that is configured to lock and unlock the housing and the tubular body; a ring member that is rotatably attached on an outer periphery of the housing and is configured to move the lock member between a lock position and an unlock position, characterized in that the ring member includes a locking portion cut and raised as an elastic element from an annular wall, said locking portion comprising an engagement projection, and in that the housing comprises a locked portion formed as a hole portion, such that when the locking portion is locked to the locked portion, the lock member is retained in the unlock position in a state where an urging force is accumulated in the lock member; when the tubular body is inserted in the housing to unlock the locking portion and release the urging force accumulated in the lock member, the engagement projection of the ring member is pushed out of the locked portion, the lock member moves to the lock position together with the ring member to lock the tubular body; and when the ring member is slid in an axis direction of the tubular body after being locked, a fitting portion provided in the ring member is fitted in a fitted portion provided in the housing to prevent rotation of the ring member, wherein, in order to release the engagement between the tubular body and the housing, first, the fitting portion is separated from the fitted portion by sliding the ring member axially, next, the ring member is rotated in an unlock direction, which causes one tip portion of the lock member to slide on a slide inclined surface included in the housing, whereby the lock member is enlarged to open in an outer peripheral direction in order to arrive to the unlock position.