A voltage equalizer which is provided in a battery pack that includes a series circuit in which more than one battery block (BT1, BT2, BT3) made of more than one unit cell is connected in series, the battery pack configured to generate a desired voltage at both ends of the series circuit, configured to equalize output voltages of the battery blocks, the voltage equalizer comprising: a discharge resistor (R1, R2, R3) provided at at least one of a positive electrode and a negative electrode of each of the battery blocks; an equalization switch (SW1, SW2, SW3) provided between the positive electrode and the negative electrode of each of the battery blocks (BT1, BT2, BT3), the equalization switch configured to switch connection and disconnection between the positive electrode and the negative electrode of each of the battery blocks through the discharge resistor; an equalization controlling unit configured to generate an equalization control signal made of a bit string of a first status signal or a second status signal that determines connection or disconnection of the equalization switch (SW1, SW2, SW3) when an equalization start command is given, and output the equalization control signal to the corresponding equalization switch so as to control connection and disconnection of the equalization switch; an equalization diagnostic unit configured to obtain an equalization detection signal of each of the battery blocks (BT1, BT2, BT3), the equalization detection signal being made of a bit string of the first status signal or the second status signal based on a voltage generated at a connection point (P1, P2, P3) of the equalization switch (SW1, SW2, SW3) and the discharge resistor (R1, R2, R3) corresponding to each of the battery blocks, also obtain the equalization control signal, and diagnose an operation status of the equalization switch based on the equalization detection signal and the equalization control signal, the equalization diagnostic unit configured to compare the equalization detection signal corresponding to the equalization switch to the equalization control signal thereby determining whether or not equalization processing is executed in conformity for each of the battery blocks based on a result of the comparison; and a latch circuit configured to output one of the first status signal and the second status signal when the equalization start command is given, and output the other one of the first status signal and the second status signal when an equalization end command is given, wherein the equalization diagnostic unit is configured to obtain a latch signal that is an output signal from the latch circuit, and is configured to determine whether or not the equalization processing for each of the battery blocks (BT1, BT2, BT3) is executed in conformity in view of the latch signal, in addition to the comparison between the equalization detection signal corresponding to the equalization switch and the equalization control signal. a discharge resistor (R1, R2, R3) provided at at least one of a positive electrode and a negative electrode of each of the battery blocks; an equalization switch (SW1, SW2, SW3) provided between the positive electrode and the negative electrode of each of the battery blocks (BT1, BT2, BT3), the equalization switch configured to switch connection and disconnection between the positive electrode and the negative electrode of each of the battery blocks through the discharge resistor; an equalization controlling unit configured to generate an equalization control signal made of a bit string of a first status signal or a second status signal that determines connection or disconnection of the equalization switch (SW1, SW2, SW3) when an equalization start command is given, and output the equalization control signal to the corresponding equalization switch so as to control connection and disconnection of the equalization switch; an equalization diagnostic unit configured to obtain an equalization detection signal of each of the battery blocks (BT1, BT2, BT3), the equalization detection signal being made of a bit string of the first status signal or the second status signal based on a voltage generated at a connection point (P1, P2, P3) of the equalization switch (SW1, SW2, SW3) and the discharge resistor (R1, R2, R3) corresponding to each of the battery blocks, also obtain the equalization control signal, and diagnose an operation status of the equalization switch based on the equalization detection signal and the equalization control signal, the equalization diagnostic unit configured to compare the equalization detection signal corresponding to the equalization switch to the equalization control signal thereby determining whether or not equalization processing is executed in conformity for each of the battery blocks based on a result of the comparison; and a latch circuit configured to output one of the first status signal and the second status signal when the equalization start command is given, and output the other one of the first status signal and the second status signal when an equalization end command is given, wherein the equalization diagnostic unit is configured to obtain a latch signal that is an output signal from the latch circuit, and is configured to determine whether or not the equalization processing for each of the battery blocks (BT1, BT2, BT3) is executed in conformity in view of the latch signal, in addition to the comparison between the equalization detection signal corresponding to the equalization switch and the equalization control signal.