Provided are a white balance adjustment device, an operation method therefor, and an operation program with which the hue of a main subject becomes appropriate at the time of capturing an image with a plurality of flashes. A non-light-emission image acquisition unit (53a) acquires a non-light-emission image (60) wherein a plurality of flash devices (12, 13) are in a non-light-emission state. A light-emission image acquisition unit (53b) acquires pre-light-emission images (61, 62) wherein the plurality of flash devices (12, 13) are respectively in an individual light-emission state. A flash irradiation area specification unit (54) specifies flash irradiation areas (67, 68) on the basis of differences between signal values of a plurality of divided areas (65) in the non-light-emission image (60) and each of the light-emission images (61, 62). A priority flash device selection unit (55) selects a priority flash device as a target for WB (white balance) adjustment. A WB adjustment unit (56) performs WB adjustment on the basis of a signal value of the irradiation area of the selected priority flash device.