A signal processing apparatus, comprising: an acquisition means configured to acquire input data having a plurality of input signals I(x) corresponding to a plurality of pixel position X respectively, and detection target data having detection target signals as a target to be detected; a noise strength setting means (3, 301) configured to set, based on the input data and the detection target data, a noise strength K used to subject the input signals I(x) to a predetermined stochastic resonance processing, the noise strength K showing the strength of noise added to the input signals I(x); and a stochastic resonance processing means (3, 301) configured to use the noise strength K set by the noise strength setting means (3, 301) and a threshold value T to quantize the input signals to subject the input signals I(x) to the predetermined stochastic resonance processing to output processed data, characterized in that the predetermined stochastic resonance processing is a processing based on a formula in which processed data J(x) is represented by I(x), the noise strength K and the threshold value T and the processed data J(x) corresponds to a result in a case where M is a large positive integer in the following formula, J x = 1 M ∑ m = 1 M j x m with j(x,m) being a result of a processing in which a value obtained by multiplying a random number noise N(x,m) of 1 to 0 by the noise strength K is added to the input signal I(x,m) and further binarized, M indicating the number of the processing among which the random number noises are different and m indicating one of the plurality processing the noise strength setting means (3, 301) sets the noise strength K based on a function of a correlation coefficient and the noise strength K, wherein the correlation coefficient showing a correlation between the result of a case where each of the plurality of input signals I(x) is subjected to the predetermined stochastic resonance processing and the detection target data, wherein the noise is white noise having an upper limit at the noise strength K set by the noise strength setting means (3, 301) or the noise is normal distribution noise having an upper limit at the noise strength K set by the noise strength setting means (3, 301). an acquisition means configured to acquire input data having a plurality of input signals I(x) corresponding to a plurality of pixel position X respectively, and detection target data having detection target signals as a target to be detected; a noise strength setting means (3, 301) configured to set, based on the input data and the detection target data, a noise strength K used to subject the input signals I(x) to a predetermined stochastic resonance processing, the noise strength K showing the strength of noise added to the input signals I(x); and a stochastic resonance processing means (3, 301) configured to use the noise strength K set by the noise strength setting means (3, 301) and a threshold value T to quantize the input signals to subject the input signals I(x) to the predetermined stochastic resonance processing to output processed data, characterized in that the predetermined stochastic resonance processing is a processing based on a formula in which processed data J(x) is represented by I(x), the noise strength K and the threshold value T and the processed data J(x) corresponds to a result in a case where M is a large positive integer in the following formula, J x = 1 M ∑ m = 1 M j x m with j(x,m) being a result of a processing in which a value obtained by multiplying a random number noise N(x,m) of 1 to 0 by the noise strength K is added to the input signal I(x,m) and further binarized, M indicating the number of the processing among which the random number noises are different and m indicating one of the plurality processing the noise strength setting means (3, 301) sets the noise strength K based on a function of a correlation coefficient and the noise strength K, wherein the correlation coefficient showing a correlation between the result of a case where each of the plurality of input signals I(x) is subjected to the predetermined stochastic resonance processing and the detection target data, wherein the noise is white noise having an upper limit at the noise strength K set by the noise strength setting means (3, 301) or the noise is normal distribution noise having an upper limit at the noise strength K set by the noise strength setting means (3, 301).