Provided are a flexible printed circuit that reduces the chance of the occurrence of short-circuit failures caused by swarf generated from punching out flexible printed circuit, and an electric circuit structure having this flexible printed circuit and an electric circuit substrate to which the flexible printed circuit is connected. A flexible printed circuit (100) has a wiring pattern (2) formed on the flexible base film (1). The flexible printed circuit (100) is individually punched out to be separated in a condition where the wiring pattern (2) is disposed on the base film (1), and the wiring pattern (2) has a narrowed portion (2c) near the edge of the base film (1).