A condition estimation device includes a voltage measurement circuit, memory, and a controller. The voltage measurement circuit measures an open circuit voltage (OCV) of an electric storage device. The memory is configured to store first information on a correlation between a positive electrode potential and an electric storage capacity and second information on a correlation between a negative electrode potential and an electric storage capacity. The controller is configured to: measure an OCV under charge or discharge; calculate an electric storage capacity of the electric storage device having the OCV equal to a reference voltage; correct at least one of the first information and the second information such that a potential difference at the calculated capacity is equal to the reference voltage; and generate an OCV characteristic based on the first and the second information after the at least one of the first and the second information is corrected.