PURPOSE: To execute 2 measurements of both systems of Fourier tramsform FT and a continuous wave signal CW, with simple constitution, by irradiating a pulselike high frequency to a sample, and measuring a free induction attenuating signal obtained from the sample.

CONSTITUTION: A nuclear magnetic resonance signal detected by a detector 1 is amplified by a high frequency amplifier 2, is detected by a phase detector 3, and is converted to a low frequency analog signal. The analog signal is converted to a digital signal through a filtering circuit 6 and an A/D converter 7, is inputted to an adder 14, and is integrated by the designated number of times. On the other hand, a clock pulse from a timer 16 is inputted to a counter 17 and the adder 14, and is inputted to the axis X of a display device 9 through the first D/A converter 11a, etc. At the same time, a signal converted to analog by the second D/A converter 11b is displayed on the axis Y of the display device 9. According to such constitution, a measurement of a CW sustem can be executed by using a mechanism of an FT system as it is, therefore, a large CW system filtering circuit is not required, and the constitution is simplified.