An electricity accumulating device comprising: a plurality of capacitors connected in series; a plurality of balanced voltage adjusting portions connected to the capacitors respectively; and a control circuit connected to the balanced voltage adjusting portions, wherein the control circuit performs following operations: measuring, by using the balanced voltage adjusting portions, a first voltage (V1i) across each of the capacitors during a non-charge-or-discharge period of the capacitors and a second voltage (V2i) across each of the capacitors during a different time; calculating an absolute value (ΔVi) of a difference between the first voltage (V1i) and the second voltage (V2i) across each of the capacitors; measuring a first point of time at which the first voltage (V1i) is measured and a second point of time at which the second voltage (V2i) is measured; calculating a time difference (Δt) by subtracting the first point of time from the second point of time; calculating a voltage adjustment range (ΔVbi) by dividing the absolute value (ΔVi) by the time difference (Δt) and multiplying a result by a specified coefficient; determining a balanced voltage (Vri) by subtracting the voltage adjustment range (ΔVbi) from an initial balanced voltage (Vro); and controlling the balanced voltage adjusting portions to make a voltage (Vi) across each of the capacitors the balanced voltage (Vri). a plurality of capacitors connected in series; a plurality of balanced voltage adjusting portions connected to the capacitors respectively; and a control circuit connected to the balanced voltage adjusting portions, wherein the control circuit performs following operations: measuring, by using the balanced voltage adjusting portions, a first voltage (V1i) across each of the capacitors during a non-charge-or-discharge period of the capacitors and a second voltage (V2i) across each of the capacitors during a different time; calculating an absolute value (ΔVi) of a difference between the first voltage (V1i) and the second voltage (V2i) across each of the capacitors; measuring a first point of time at which the first voltage (V1i) is measured and a second point of time at which the second voltage (V2i) is measured; calculating a time difference (Δt) by subtracting the first point of time from the second point of time; calculating a voltage adjustment range (ΔVbi) by dividing the absolute value (ΔVi) by the time difference (Δt) and multiplying a result by a specified coefficient; determining a balanced voltage (Vri) by subtracting the voltage adjustment range (ΔVbi) from an initial balanced voltage (Vro); and controlling the balanced voltage adjusting portions to make a voltage (Vi) across each of the capacitors the balanced voltage (Vri). measuring, by using the balanced voltage adjusting portions, a first voltage (V1i) across each of the capacitors during a non-charge-or-discharge period of the capacitors and a second voltage (V2i) across each of the capacitors during a different time; calculating an absolute value (ΔVi) of a difference between the first voltage (V1i) and the second voltage (V2i) across each of the capacitors; measuring a first point of time at which the first voltage (V1i) is measured and a second point of time at which the second voltage (V2i) is measured; calculating a time difference (Δt) by subtracting the first point of time from the second point of time; calculating a voltage adjustment range (ΔVbi) by dividing the absolute value (ΔVi) by the time difference (Δt) and multiplying a result by a specified coefficient; determining a balanced voltage (Vri) by subtracting the voltage adjustment range (ΔVbi) from an initial balanced voltage (Vro); and controlling the balanced voltage adjusting portions to make a voltage (Vi) across each of the capacitors the balanced voltage (Vri).