A selectable one-way clutch adapted to prevent an undesirable engagement is provided. The selectable one-way clutch comprises first spline teeth formed on a connecting portion of a notch plate connected to a rotary member; second spline teeth formed on the rotary member to be meshed with the first spline teeth; a first flank formed individually on the first spline teeth; and a second flank formed individually on the second spline teeth to be brought into contact to the first flank. The first flank and the second flank are individually set at a predetermined angle to establish a component of torque of the rotary member rotating the notch plate to isolate the notch plate away from the selector plate.