This freezer control device (74) is provided with: a storage unit (18) which stores operation data detected at each site in a turbo freezer; a compression unit (34) which, when the size of the operation data accumulated over time in the storage unit (18) becomes too large, converts the operation data each time a condition depending on the type of operation data is met, thereby compressing the data size; and a diagnostic unit (36) which evaluates the state of the turbo freezer on the basis of the operation data converted by the compression unit (34). By this means, the state of the freezer can be diagnosed without increasing the storage capacity of the storage medium that stores operation data of the turbo freezer.