1. An automatic programming method having an NC creation program-editing function for editing an NC creation program including a plurality of machining units and a machining program for each machining unit by using a program editing screen, the program editing screen including: a machining shape tree on which a plurality of machining unit names indicating a machining shape of the machining unit, as a unit of machining in which continuous machining is performed with the same main spindle and with the same tool, is displayed hierarchically according to a machining order; a program tree on which a plurality of machining program names relating to the respective machining units is displayed hierarchically according to the machining order; an editor section in which machining unit data corresponding to one of the machining unit names specified on the machining shape tree including machining shape information indicating the machining shape and machining content data indicating machining contents, and the machining program corresponding to one of the machining program names specified on the program tree are displayed to perform editing; and a model display section in which a product model, a work model, and a machining shape model corresponding to a machining unit that corresponds to the one of the machining unit names are displayed three-dimensionally, comprising: automatically inserting machining shape information corresponding to a specified shape element required for forming the machining unit data with respect to the machining shape model displayed in the model display section in a cursor position specified in the editor section, wherein the inserted machining shape information indicates the machining shape of the machining unit that machines the work model into the product model and a machining area of the machining unit specified in the machining program.