A data processor for analyzing chromatograms in detail and collecting analysis-associated information necessary for verification of data validity throughout an analysis process. The data processor includes a first data collecting section which collects and records a detector output at every data sampling rate T1 for each sample injection, and a second data collecting section which collects and records the detector output and a monitor output indicating an analysis-associated condition at every data sampling rate T2 over a period from the start to the end of the chromatographic analysis; the data sampling rate T1 is shorter than the data sampling rate T2.