A selectable one-way clutch comprising: a pocket plate having multiple accommodating recessed portions in one surface of an annular plate portion of the pocket plate; an annular notch plate configured to be relatively rotatable with respect to the pocket plate, the notch plate being provided with multiple engagement recessed portions on a surface thereof opposite to the surface of the pocket plate in which the accommodating recessed portions are provided; plate-like engagement pieces accommodated in the accommodating recessed portions; and an annular cover plate being fixed to the pocket plate in a state in which the cover plate faces the surface of the pocket plate provided with the accommodating recessed portions of the pocket plate, the cover plate having multiple through-holes through which one end portions of the engagement pieces project toward an engagement recessed portion side, the selectable one-way clutch being characterised by the one end portions of the engagement pieces including engagement surfaces configured to be engaged with the engagement recessed portions, and projecting portions configured to project in a length direction of the engagement pieces from the engagement surfaces so as to come into contact with one surface of the cover plate, the engagement pieces being configured such that in a state in which the projecting portions are in contact with one surface of the cover plate, the engagement surfaces come into an erect state in which the engagement surfaces project toward the notch plate side from the other surface of the cover plate, at least one of the pocket plate and the notch plate being configured to move in a rotation axis direction of the notch plate, and by changing a distance in an axial direction between the pocket plate and the notch plate, the selectable one-way clutch being configured to carry out switching between an out-of-engagement state in which the engagement pieces in the erect state are out of engagement with the engagement recessed portions and a one-way clutch state in which the engagement pieces in the erect state come into engagement with the engagement recessed portions. a pocket plate having multiple accommodating recessed portions in one surface of an annular plate portion of the pocket plate; an annular notch plate configured to be relatively rotatable with respect to the pocket plate, the notch plate being provided with multiple engagement recessed portions on a surface thereof opposite to the surface of the pocket plate in which the accommodating recessed portions are provided; plate-like engagement pieces accommodated in the accommodating recessed portions; and an annular cover plate being fixed to the pocket plate in a state in which the cover plate faces the surface of the pocket plate provided with the accommodating recessed portions of the pocket plate, the cover plate having multiple through-holes through which one end portions of the engagement pieces project toward an engagement recessed portion side, the selectable one-way clutch being characterised by the one end portions of the engagement pieces including engagement surfaces configured to be engaged with the engagement recessed portions, and projecting portions configured to project in a length direction of the engagement pieces from the engagement surfaces so as to come into contact with one surface of the cover plate, the engagement pieces being configured such that in a state in which the projecting portions are in contact with one surface of the cover plate, the engagement surfaces come into an erect state in which the engagement surfaces project toward the notch plate side from the other surface of the cover plate, at least one of the pocket plate and the notch plate being configured to move in a rotation axis direction of the notch plate, and by changing a distance in an axial direction between the pocket plate and the notch plate, the selectable one-way clutch being configured to carry out switching between an out-of-engagement state in which the engagement pieces in the erect state are out of engagement with the engagement recessed portions and a one-way clutch state in which the engagement pieces in the erect state come into engagement with the engagement recessed portions.