A machining time-estimating method for a wire electrical discharge machine for estimating the remaining machining time (Tr) during the machining of a workpiece comprises: a step for setting a predicted machining velocity; a step for determining the actual machining velocity; a step for determining an estimated machining velocity so as to incorporate the predicted machining velocity and the actual machining velocity at a specified ratio, that is, a reference ratio; and a step for calculating remaining machining time from the estimated machining velocity. By executing the actual machining velocity-determining step to the remaining machining time-calculating step repeatedly to estimate remaining machining time moment by moment, remaining wire electrical discharge machining time is estimated with reduced error.