A cache device may include a first storage unit configured to store first cache data, a second storage unit configured to store a cache file that stores copy of the first cache data as second cache data; a reading unit configured to select and read out one of the first cache data, which has been stored in the first storage unit, and the second cache data, which has been stored in the cache file stored in the second storage unit, in response to a reference request from outside, and an instructing unit configured to determine probability of expecting future referencing request based on the frequency of past referencing requests, the instructing unit being configured to instruct that either the first cache data or the second cache data is to be selected and read out based on the probability.