A tool comprising: a holder configured to hold a bit; and an oscillating rotary mechanism configured to impart an oscillating rotary motion to the holder, the holder including a holding surface, a securing portion, and an elastic mechanism, in a holding state where the bit is held by the holder, the bit being placed on top of the holding surface, the securing portion being engaged with an attachment portion that forms part of the bit, the elastic mechanism applying elastic force to the securing portion, and wherein the securing portion is movable in a direction aligned with the holding surface, a direction in which the elastic force is applied in the holding state agrees with a component, directed toward the attachment portion, of the direction, the securing portion has a securing surface facing toward the holding surface, in the holding state, the securing portion is engaged with the attachment portion by bringing the securing surface into contact with the attachment portion and applies the force directed toward the holding surface from the securing surface to the attachment portion, the elastic mechanism includes a supporting portion leading to the securing portion, the elastic mechanism produces, when elastically deformed at least partially, elastic force and applies the elastic force to the securing portion, and the elastic force applied by the elastic mechanism to the securing portion is produced by elasticity of the supporting portion, said tool being characterised by: the securing portion applying force, resultant from the elastic force and directed toward the holding surface, to the attachment portion; and wherein the securing surface is sloping away from the holding surface. a holder configured to hold a bit; and an oscillating rotary mechanism configured to impart an oscillating rotary motion to the holder, the holder including a holding surface, a securing portion, and an elastic mechanism, in a holding state where the bit is held by the holder, the bit being placed on top of the holding surface, the securing portion being engaged with an attachment portion that forms part of the bit, the elastic mechanism applying elastic force to the securing portion, and wherein the securing portion is movable in a direction aligned with the holding surface, a direction in which the elastic force is applied in the holding state agrees with a component, directed toward the attachment portion, of the direction, the securing portion has a securing surface facing toward the holding surface, in the holding state, the securing portion is engaged with the attachment portion by bringing the securing surface into contact with the attachment portion and applies the force directed toward the holding surface from the securing surface to the attachment portion, the elastic mechanism includes a supporting portion leading to the securing portion, the elastic mechanism produces, when elastically deformed at least partially, elastic force and applies the elastic force to the securing portion, and the elastic force applied by the elastic mechanism to the securing portion is produced by elasticity of the supporting portion, said tool being characterised by: the securing portion applying force, resultant from the elastic force and directed toward the holding surface, to the attachment portion; and wherein the securing surface is sloping away from the holding surface. the securing portion applying force, resultant from the elastic force and directed toward the holding surface, to the attachment portion; and wherein the securing surface is sloping away from the holding surface.