The invention discloses an apparatus and method for estiamating available power of a high voltage battery. The apparatus for estimating an available power of a high voltage battery includes: a memory that stores a table recording an available power corresponding to a state of charge (SoC) value of the high voltage battery; a voltage sensor that measures a voltage of the high voltage battery; a current sensor equipped with a first module for measuring a low current of the high voltage battery and a second module for measuring a high current; and a controller that estimates an available power by using the voltage and the low current, or the voltage and the high current, when the voltage sensor is normal, and search an available power corresponding to a SoC value after calculating the SoC value by using the low current or the high current when the voltage sensor is broken.