1. An image analysis device comprising: a radiographic image acquisition section that acquires a radiographic image acquired by radiography; a dosage data acquisition section that acquires dosage data indicating, in a time-series manner, a dosage of radiation rays exposed to a specific position in an imaging area corresponding to the radiographic image in a specific period including an imaging period of the radiographic image; and a determining section that determines whether the dosage data has a first feature indicating a dosage variation as a plurality of radiation absorbing bodies and a radiation transmitting body disposed between adjacent radiation absorbing bodies pass through a space between the specific position and a radiation source used for the radiography, and determines that the radiographic image corresponding to the dosage data determined to have the first feature is a rocking grid use image captured by rocking a rocking imaging grid for removing scattered rays.