To precisely estimate a constant noise component included in a collection signal.

A constant noise model estimation section 14 estimates the constant noise component included in a present collection signal which is a collection signal at a certain time, by updating an estimation result of the constant noise component which is estimated on the basis of a past collection signal that is a past collection signal from that time. A constant noise model update coefficient setting section 13 controls estimation of the constant noise component, on the basis of a non-constant index that is an index in which an estimation rate of the non-constant signal component included in the present collection signal is expressed by a value size. In controlling the estimation, a change amount by the update of the estimation result of the constant noise component estimated on the basis of the past collection signal is set smaller, when the non-constant index is a prescribed threshold or more, than that when the non-constant index is smaller than the threshold.