The electric rail power supply system analysis device is the first to derive the first admittance matrix by expressing the currents supplied to the Scott transformer in consideration of the leakage impedance of the Scott transformer as a formula for the voltage supplied to the Scott transformer and the voltage output from the Scott transformer. An admittance matrix derivation unit, a second admittance matrix derivation unit that derives a second admittance matrix by expressing the currents output from the autotransformer as a formula for voltages output from the autotransformer in consideration of the magnetization impedance and leakage impedance of the autotransformer; and It includes a power flow calculation unit that performs power flow calculation by substituting the first admittance matrix and the second admittance matrix into the relationship between the current error vector and the voltage error vector derived through the three-phase current injection technique applied to the electric railway power supply system.