A screen transition diagram creator that creates a screen transition diagram illustrating complicated transition relations in an easy-to-understand manner, including: a screen transition diagram editor providing the screen transition diagram in which transition relations among plural screens are illustrated by plural screen nodes and arrows between the screen nodes; a screen transition pattern applying unit applying a predetermined screen transition pattern to a target screen node group that includes at least part of the screen nodes illustrated in the screen transition diagram to provide a pattern-applied screen node group; and a screen transition structure diagram creator creating a screen transition structure diagram by abridgement processing on the pattern-applied screen node group according to a display layout corresponding to the screen transition pattern. In the abridgement processing, arrows are deleted and an icon that simplistically illustrates a transition pattern between the screen nodes displayed in the display layout is added.