A female circuit board for use with a male circuit board has electrically conductive projections. The female circuit board includes a flexible insulating film. The flexible insulating film includes insertion portions into which the conductive projections of the male circuit board are allowed to be inserted. Each of the insertion portions includes a plurality of slits communicating with each other at the center of each of the insertion portions. The flexible insulating film further includes electrically conduction portions for making contact with the conductive projections to come into conduction with the male circuit board. The conduction portions are disposed around the insertion portions on the surface of the female circuit board facing the male circuit board when the female circuit board is in contact with the male circuit board. The conduction portions conform in shape to the insertion portions.