By accurately estimating the survival cell count in a probiotic product, the time for developing the product can be shortened. In a device (1) for estimating survival cell count, a calculation unit (14) calculates an estimated result of the survival cell count nt (CFU/g) of a specific strain contained in a composition after storage, in accordance with the following equation (I). (I) Log10nt=Log10n0−t×EXP{(AT×T+BT)w+(CT×T+DT)}, provided that t stands for the storage period (days)× 1/30, nt stands for the survival cell count (CFU/g) of the strain contained in the composition after the storage period t (days), n0 stands for the viable cell count (CFU/g) of the strain contained in the composition at the initiation of storage, T stands for the storage temperature (° C.), w stands for the water activity value of the composition, AT and CT stand for experimentally determined coefficients specific to the strain, and BT and DT stand for experimentally determined constants specific to the strain.