A method for estimating a machining time of a wire electrical discharge machine which estimates a remaining machining time while machining a workpiece, the method comprising steps of: setting a predicted machining speed; finding an actual machining speed; determining an estimated machining speed so that a ratio of referring to the predicted machining speed, defined as a predicted machining speed reference rate, and a ratio of referring to the actual machining speed, defined as an actual machining speed reference rate, respectively become predetermined values, wherein the predicted machining speed reference rate falls along with progression of the machining and the actual machining speed reference rate increases along with progression of the machining such that, when machining is proceeding in a first predetermined time period right after a start of machining or in a first predetermined section of the workpiece, the predicted machining speed reference rate is made 100%, when machining is proceeding in a second predetermined time period after an elapse of the first predetermined time period or in a second predetermined section after the first predetermined section is passed, the predicted machining speed reference rate is gradually lowered and the actual machining speed reference rate is gradually raised in accordance with progression of the machining, and, when machining is proceeding in a third predetermined time period after an elapse of the second predetermined time period or in a third predetermined section after the second predetermined section is passed, a predetermined lower limit reference rate is applied for the predicted machining speed reference rate and a predetermined upper limit reference rate is applied for the actual machining speed reference rate; and calculating the remaining machining time from the estimated machining speed, wherein the remaining machining time at each instant being estimated by repeatedly executing the process from the step of finding the actual machining speed to the step of calculating the remaining machining time. setting a predicted machining speed; finding an actual machining speed; determining an estimated machining speed so that a ratio of referring to the predicted machining speed, defined as a predicted machining speed reference rate, and a ratio of referring to the actual machining speed, defined as an actual machining speed reference rate, respectively become predetermined values, wherein the predicted machining speed reference rate falls along with progression of the machining and the actual machining speed reference rate increases along with progression of the machining such that, when machining is proceeding in a first predetermined time period right after a start of machining or in a first predetermined section of the workpiece, the predicted machining speed reference rate is made 100%, when machining is proceeding in a second predetermined time period after an elapse of the first predetermined time period or in a second predetermined section after the first predetermined section is passed, the predicted machining speed reference rate is gradually lowered and the actual machining speed reference rate is gradually raised in accordance with progression of the machining, and, when machining is proceeding in a third predetermined time period after an elapse of the second predetermined time period or in a third predetermined section after the second predetermined section is passed, a predetermined lower limit reference rate is applied for the predicted machining speed reference rate and a predetermined upper limit reference rate is applied for the actual machining speed reference rate; and calculating the remaining machining time from the estimated machining speed, wherein the remaining machining time at each instant being estimated by repeatedly executing the process from the step of finding the actual machining speed to the step of calculating the remaining machining time.