A detent escapement for a mechanical timepiece includes an escape wheel, a balance mounted for undergoing oscillation movement about a balance staff, a blade and an actuating spring. The balance has an unlocking stone and has an impulse jewel for contacting a wheel tooth of the escape wheel. The blade has a locking stone for contacting the wheel tooth of the escape wheel and is supported for undergoing movement in approaching and separating directions relative to the escape wheel. The actuating spring is configured to contact the unlocking stone and is mounted for undergoing elastic deformation along the approaching and separating directions with respect to the blade. An adjustment mechanism adjusts a projecting amount of a spring tip portion of the actuating spring from a blade tip portion of the blade.