To perform accurate measurement in the analysis of chemical components with low concentration, pretreatment such as concentration and purification of samples is essential. For high-throughput of pretreatment of biological samples, various random clinical testing is encountered, where analytes change from sample to sample. The pretreatment apparatus has a separating agent selectively separating a specific component by allowing a sample solution to flow therethrough. A holding section holds a plurality of housing sections, which house the separating agent therein, and has an endless track. A pressurizing section applies pressure to the housing section in a continuous and random-accessible manner; and an extraction solution receiver mechanism selectively receives an extracted solution from the separating agent housed in the housing section. A mass spectrometer is that can be connected to the pretreatment apparatus. Thus, a large number of specimens can be simultaneously processed.