Noise floor level reduction device and noise floor level reduction method

Provided are a noise floor level reduction device and a noise floor level reduction method capable of reducing a noise floor level. A transmission power measurement system 10 is installed before a signal measurement device 20 including a noise floor level measurement unit 22 that measures a noise floor level, and a measurement unit 24 that subtracts the noise floor level from a level of a signal from a DUT 2 to calculate a level of a signal after subtraction, and includes an LNA 17 provided between the DUT 2 and the signal measurement device 20 for amplifying the signal from the DUT 2, and a termination resistor 16 that terminates an input of the LNA 17, and the termination resistor 16 terminates the input of the LNA 17 in a case in which the noise floor level measurement unit 22 measures the noise floor level.