A phase compensation apparatus in a line-to-line voltage in a system including an inverter configured to supply a voltage to a motor, a controller configured to supply a command voltage to the inverter and a voltage detection unit configured to detect an inverter output voltage, the apparatus comprising: a conversion unit configured to convert 3-phase voltage information measured by the voltage detection unit into a d-axis voltage and a q-axis voltage of a stationary coordinate system; a first determination unit configured to determine a size of the command voltage based on d-axis and q-axis command voltages in the stationary coordinate system; and a second determination unit configured to determine a size of the inverter output voltage using the output voltage of the conversion unit; characterized by a first normalization unit configured to calculate a phase of the command voltage in sine and cosine form by normalizing the command voltage using the size of the command voltage, which is an output of the first determination unit; a first conversion unit configured to convert the output voltages of the conversions unit from the stationary coordinate system into a rotary coordinate system using the phase of the command voltage in sine and cosine form; a second normalization unit configured to calculate a phase error between the inverter output voltage and the command voltage by normalizing the inverter output voltage converted into the rotary coordinate system to the size of the inverter output voltage which is an output of the second determination unit; and a second conversion unit configured to output a compensation voltage by converting the output voltages of the conversion unit from the stationary coordinate system into a rotary coordinate system using the phase error in sine and cosine form, wherein the size of the compensation voltage which is an output of the second conversion unit is the same as that of the inverter output voltage, and the phase of the compensation voltage is the same as that of the command voltage. a conversion unit configured to convert 3-phase voltage information measured by the voltage detection unit into a d-axis voltage and a q-axis voltage of a stationary coordinate system; a first determination unit configured to determine a size of the command voltage based on d-axis and q-axis command voltages in the stationary coordinate system; and a second determination unit configured to determine a size of the inverter output voltage using the output voltage of the conversion unit; characterized by a first normalization unit configured to calculate a phase of the command voltage in sine and cosine form by normalizing the command voltage using the size of the command voltage, which is an output of the first determination unit; a first conversion unit configured to convert the output voltages of the conversions unit from the stationary coordinate system into a rotary coordinate system using the phase of the command voltage in sine and cosine form; a second normalization unit configured to calculate a phase error between the inverter output voltage and the command voltage by normalizing the inverter output voltage converted into the rotary coordinate system to the size of the inverter output voltage which is an output of the second determination unit; and a second conversion unit configured to output a compensation voltage by converting the output voltages of the conversion unit from the stationary coordinate system into a rotary coordinate system using the phase error in sine and cosine form, wherein the size of the compensation voltage which is an output of the second conversion unit is the same as that of the inverter output voltage, and the phase of the compensation voltage is the same as that of the command voltage.