An ultrasonic cleaning device for cleaning a fuel assembly constituting an item to be cleaned, includes: a plurality of ultrasonic transducers which irradiate the outside of this item to be cleaned with ultrasonic waves from at least two directions; an ultrasonic transducer translating mechanism which moves ultrasonic transducers vertically along a support member and which is provided with a steel housing constituting an ultrasonic wave reflecting structure which reflects ultrasonic waves from ultrasonic transducers towards the item to be cleaned a feed pump arranged outside the item to be cleaned and constituting a cleaning liquid supply mechanism which supplies cleaning liquid in a pressurized condition into the interior of the item to be cleaned; and a discharge pump including a cleaning liquid discharge mechanism that discharges cleaning liquid from the cleaning liquid supply mechanism to a filter device.