PROBLEM TO BE SOLVED: To provide a flexible printed circuit board capable of enlarging intervals of mutually adjacent conductor parts while inhibiting enlargement of the width in an elevation direction of an ultrasonic probe.SOLUTION: A flexible printed circuit board 50 includes a plurality of conductor parts 52 that are electrically connected to a plurality of ultrasonic transducers disposed in an azimuth direction in a housing of an ultrasonic probe, and are formed at required intervals X1. The flexible printed circuit board 50 is provided in the housing so as to be pulled out in the azimuth direction, and includes a narrow width portion 55 that has a minimum width or less in the elevation direction in an inner space at the end of the housing in a contact surface side with a subject, and wide width portions 56 that are formed on both sides of the narrow width portion 55 and have the width larger than that of the narrow width portion 55.
