A current sensing circuit configured to sense current flowing through a switching transistor of a non-insulated switching regulator, the current sensing circuit includes a voltage divider circuit portion; a first transistor; a first impedance element; a second transistor; a third transistor; and a first voltage comparing circuit portion, wherein control terminals of the first transistor, the second transistor, and the third transistor are connected to each other and a connecting portion of the control terminals is connected to a connecting portion between the third transistor and the first constant current source.