It is possible to provide a compression ratio data compression device, a data compression program, and an imaging device which can estimate a compression degree in a short processing time. The data compression device includes: a difference generation unit which processes continuous numeric values constituting data to be compressed, i.e., obtains a difference between adjacent numeric values which are adjacent to each other directly or at a constant distance so as to generate new data-to-be-compressed which is formed by continuous numeric values indicating the differences; a compression unit which executes a compression process on the data-to-be-compressed generated by the difference generation unit; and an estimation unit which acquires concentration degrees of the respective numeric values constituting the data-to-be-compressed generated by the difference generation unit to a numeric value expressing a difference ''0'' and higher estimates the compression degree when the data-to-be-compressed is compressed by the compression unit as the concentration degree increases.