Overlock sewing machine

An overlock sewing machine comprising:

• a switching member configured to switch, between a threading state and a sewing-enabled state, a threading mechanism provided to a sewing machine main body so as to support threading for a looper;
• a looper cover coupled to a hinge shaft arranged on a front side of the threading mechanism with a left-right direction as an axial direction thereof, such that it can be operated to switch between an open state and a closed state;
• a side cover coupled to the sewing machine main body such that it is positioned on one side with respect to the threading mechanism defined in the left-right direction and such that it can be operated to switch between an open state and a closed state;
• a switch comprising an operating protrusion, and configured such that, when the operating protrusion is pressed, the switch detects the closed state of the looper cover, the closed state of the side cover, and the sewing-enabled state of the threading mechanism;
• a looper cover detection member configured to operate such that it is moved from a non-switching position to a switching position according to a transition of the looper cover from the open state to the closed state, and such that, after the looper cover detection member reaches the switching position, the looper cover detection member operates the switching member so as to switch the threading mechanism to the sewing-enabled state;
• a side cover detection member configured to operate such that it is moved from a non-detection position to a detection position according to a transition of the side cover from the open state to the closed state;
• and
• a lever coupled to the looper cover detection member and the side cover detection member, and configured to switch between a pressing state in which it presses the operating protrusion and a non-pressing state in which it does not press the operating protrusion, according to an operating state of the looper cover detection member and an operating state of the side cover detection member,
• wherein, when the looper cover detection member is moved to a switching position and the side cover detection member is moved to a detection position, the lever is set to the pressing state.