A voltage detection device comprising: a differential amplification circuit configured to include a first input terminal (V1in) configured to receive a first voltage of power supplied from a battery, a second input terminal (V2in) configured to receive a second voltage of the power that is a voltage different from the first voltage and is supplied from the battery, an amplification circuit (OP1 to OP3) configured to amplify a differential voltage between the first voltage received from the first input terminal (V1in) and the second voltage received from the second input terminal (V2in) at an amplification factor, and an output terminal (V3out) configured to output the differential voltage amplified by the amplification circuit (OP1 to OP3); and a control circuit configured to detect the differential voltage output from the differential amplification circuit and calculate an internal resistance value of the battery based on the differential voltage; characterized in that the differential amplification circuit is configured to include an amplification factor adjustment circuit capable of adjusting the voltage amplification factor; the amplification circuit (OP1 to OP3) is configured to amplify the differential voltage between the first voltage and the second voltage at the amplification factor adjusted by the amplification factor adjustment circuit; the control circuit is configured to control the amplification factor adjustment circuit, wherein the control circuit is configured to control the amplification factor adjustment circuit based on a maximum voltage representing a highest voltage detectable by the control circuit and the differential voltage output from the output terminal (V3out) so as to set the amplification factor of the amplification circuit (OP1 to OP3). a differential amplification circuit configured to include a first input terminal (V1in) configured to receive a first voltage of power supplied from a battery, a second input terminal (V2in) configured to receive a second voltage of the power that is a voltage different from the first voltage and is supplied from the battery, an amplification circuit (OP1 to OP3) configured to amplify a differential voltage between the first voltage received from the first input terminal (V1in) and the second voltage received from the second input terminal (V2in) at an amplification factor, and an output terminal (V3out) configured to output the differential voltage amplified by the amplification circuit (OP1 to OP3); and a control circuit configured to detect the differential voltage output from the differential amplification circuit and calculate an internal resistance value of the battery based on the differential voltage; characterized in that the differential amplification circuit is configured to include an amplification factor adjustment circuit capable of adjusting the voltage amplification factor; the amplification circuit (OP1 to OP3) is configured to amplify the differential voltage between the first voltage and the second voltage at the amplification factor adjusted by the amplification factor adjustment circuit; the control circuit is configured to control the amplification factor adjustment circuit, wherein the control circuit is configured to control the amplification factor adjustment circuit based on a maximum voltage representing a highest voltage detectable by the control circuit and the differential voltage output from the output terminal (V3out) so as to set the amplification factor of the amplification circuit (OP1 to OP3).