To provide a digital orthogonal lock-in detecting method and device capable of receiving a signal in magnetic resonance at high sensitivity.

In the method of digitally and orthogonally receiving a signal in the magnetic resonance or electron spin resonance, digitized signal wave is multiplied by digitized reference wave of sine function and cosine function to obtain a signal of a real part and imaginary part having different phases by 90°, the frequencies of the sine function and cosine function are varied according to observation width, and operation of multiplying reference wave over a plurality of times is repeated.