A state of charge estimation device (20, 62) for estimating a state of charge of an electric storage device, the state of charge estimation device (20, 62) comprising: a memory configured to store data on a first correlation between an elapsed time since an end of charge/discharge of the electric storage device and an estimation error in estimation of the state of charge; and a controller component configured to: execute, when the electric storage device is in a non-charge/discharge state, a first estimation process for estimating a first state of charge and a first estimation error (ΔC1) of the electric storage device based on a terminal voltage of the electric storage device in the non-charge/discharge state and the elapsed time; and execute, when the electric storage device is in a charge/discharge state, a second estimation process for estimating a second state of charge and a second estimation error (ΔC2) of the electric storage device based on an accumulated charge/discharge current of the electric storage device in the charge/discharge state, wherein the controller component is further configured to: calculate, in the first estimation process, a total error (ΔCS) from the first estimation error (ΔC1) and the second estimation error (ΔC2); and estimate, in the first estimation process, the first estimation error (ΔC1) and the first state of charge when the elapsed time becomes equal to or longer than a reference time, wherein the reference time is defined based on the total error (ΔCS) and the first correlation. a memory configured to store data on a first correlation between an elapsed time since an end of charge/discharge of the electric storage device and an estimation error in estimation of the state of charge; and a controller component configured to: execute, when the electric storage device is in a non-charge/discharge state, a first estimation process for estimating a first state of charge and a first estimation error (ΔC1) of the electric storage device based on a terminal voltage of the electric storage device in the non-charge/discharge state and the elapsed time; and execute, when the electric storage device is in a charge/discharge state, a second estimation process for estimating a second state of charge and a second estimation error (ΔC2) of the electric storage device based on an accumulated charge/discharge current of the electric storage device in the charge/discharge state, execute, when the electric storage device is in a non-charge/discharge state, a first estimation process for estimating a first state of charge and a first estimation error (ΔC1) of the electric storage device based on a terminal voltage of the electric storage device in the non-charge/discharge state and the elapsed time; and execute, when the electric storage device is in a charge/discharge state, a second estimation process for estimating a second state of charge and a second estimation error (ΔC2) of the electric storage device based on an accumulated charge/discharge current of the electric storage device in the charge/discharge state, wherein the controller component is further configured to: calculate, in the first estimation process, a total error (ΔCS) from the first estimation error (ΔC1) and the second estimation error (ΔC2); and estimate, in the first estimation process, the first estimation error (ΔC1) and the first state of charge when the elapsed time becomes equal to or longer than a reference time, wherein the reference time is defined based on the total error (ΔCS) and the first correlation. calculate, in the first estimation process, a total error (ΔCS) from the first estimation error (ΔC1) and the second estimation error (ΔC2); and estimate, in the first estimation process, the first estimation error (ΔC1) and the first state of charge when the elapsed time becomes equal to or longer than a reference time, wherein the reference time is defined based on the total error (ΔCS) and the first correlation.