An apparatus and a method for controlling a motor are provided. The apparatus for controlling a motor includes a temperature sensor that is configured to detect a temperature of an inverter, and a variable amplifier that is configured to variably set an amplification gain that corresponds to the detected temperature of the inverter and amplify and output a resolver signal output from a resolver based on the variably set amplification gain, based on an excitation signal. A controller is then configured to estimate a position of a motor rotor based on the amplified resolver signal to calculate a flux angle and an excitation signal generator is configured to generate the excitation signal that corresponds to the calculated flux angle and output the generated excitation signal to the resolver.