A battery state estimation device for estimating a charged electric charge quantity of a rechargeable battery, the charged electric charge quantity being a value calculated from a total capacity of the battery and a state of charge, i.e. SOC, wherein the charged electric charge quantity, the total capacity of the battery, and the SOC have a relationship expressed as "charged electric charge quantity = total battery capacity × SOC", the battery state estimation device comprising: an impedance measurement unit configured to measure a plurality of complex impedances of the rechargeable battery by supplying measurement power to the rechargeable battery; characterised in that the battery state estimation device further comprises: a parameter calculation unit configured to calculate a parameter that includes a ratio of a difference between measurement angular velocities, wherein the measurement angular velocities and the measurement frequencies have a relationship of "angular velocity = 2π × frequency",, of two complex impedances in a frequency range corresponding to a diffusion region among the measured complex impedances to a difference between components of the two complex impedances; and an electric charge quantity estimation unit configured to estimate a charged electric charge quantity of the rechargeable battery based on the calculated parameter and preset correlated information between the charged electric charge quantity of the rechargeable battery and the parameter. an impedance measurement unit configured to measure a plurality of complex impedances of the rechargeable battery by supplying measurement power to the rechargeable battery; characterised in that the battery state estimation device further comprises: a parameter calculation unit configured to calculate a parameter that includes a ratio of a difference between measurement angular velocities, wherein the measurement angular velocities and the measurement frequencies have a relationship of "angular velocity = 2π × frequency",, of two complex impedances in a frequency range corresponding to a diffusion region among the measured complex impedances to a difference between components of the two complex impedances; and an electric charge quantity estimation unit configured to estimate a charged electric charge quantity of the rechargeable battery based on the calculated parameter and preset correlated information between the charged electric charge quantity of the rechargeable battery and the parameter. a parameter calculation unit configured to calculate a parameter that includes a ratio of a difference between measurement angular velocities, wherein the measurement angular velocities and the measurement frequencies have a relationship of "angular velocity = 2π × frequency",, of two complex impedances in a frequency range corresponding to a diffusion region among the measured complex impedances to a difference between components of the two complex impedances; and an electric charge quantity estimation unit configured to estimate a charged electric charge quantity of the rechargeable battery based on the calculated parameter and preset correlated information between the charged electric charge quantity of the rechargeable battery and the parameter.