A detent escapement for a timepiece capable of decreasing energy loss with respect to a free oscillation of a balance and improving a timekeeping accuracy is provided. In addition, a detent escapement of a timepiece capable of realizing miniaturization and suppressing variations in the accuracy of a finished product due to assembly errors is provided. A one-side actuating spring of a detent 7 is formed so that a maximum stress portion, which is generated at the time of operating due to the contact of an unlocking stone 4 when a balance 5 is return-rotated, is present to be perpendicular to a first straight line L1 which connects the center of the balance staff 9 and a fulcrum 23a of the blade 23, and to be the side opposite to the balance by a second straight line L2 which passes through the fulcrum 23a.