1. In a machining time display method for displaying, in the form of bar graphs, machining times of each tool rest for every synchronized process in a simultaneous four-axis lathe in which there is provided first and second NC programs corresponding to first and second tool rests, wherein the first and second NC programs have queuing commands, wherein a workpiece is machined by controlling movement of the first and second tool rests independently in accordance with the first and second NC programs, respectively, while synchronization is achieved by said queueing commands, said method comprising the steps of: (a) obtaining a total machining time T.sub.m of machining performed by the simultaneous four-axis lathe by determining and storing machining times T.sub.1i, T.sub.2i for each synchronized process of the first and second tool rests and using the longer of the machining times of each of the synchronized processes which are carried out simultaneously by both the first and second tool rest to calculate the total machining time T.sub.m ; (b) calculating machining time per character by dividing said total machining time T.sub.m by a number of characters C used for bar graph display; (c) determining a number of characters necessary for displaying the machining time of each synchronized process by dividing the machining time of each of the synchronized processes by the obtained machining time per character; and (d) displaying the machining time for each of the first and second tool rests in the form of a bar graph by allotting patterns for bar graph display stored beforehand in a character generator to the calculated numbers of characters and respective machining times.