To provide a continuous monitoring method and a continuous monitoring apparatus of a specimen component concentration, comprising a filtering means capable of improving accuracy by removing a noise signal included in a measuring signal.

A value taken by a measurement variation quantity for indicating a correlation with the concentration being a monitoring object, is measured at a plurality of times juxtaposed in time series, to be set as a measuring signal zt. An error caused by noise in the measuring signal zt included in a useful signal yt by using filtering algorithm of a time area in the useful signal representing a variation in a specific period of the concentration. At this time, a degree of an actually measured measured value contributing to specifying the useful signal yt is designated to the filtering algorithm by a weight factor Vt. A signal difference parameter σt is calculated on the basis of a signal difference related to the measured value acquired in a period in the vicinity of time for performing actual measurement.