Disclosed is a sample treatment apparatus which can subject a filtrate obtained after a reaction treatment to a solid phase extraction treatment without the need of carrying out a primary collection of the filtrate. A necessary amount of a solid phase extracting agent (308) is added to a solid phase extraction instrument (303) to carry out conditioning. An aqueous solution is added to the solid phase extracting agent (308), and a supernatant is discarded. A filter instrument (302) is attached to an opening of the solid phase extraction instrument (303), and a sample is added to a filter reservoir (304). A hemolyzing agent is added to the sample, and the resulting mixture is fully agitated to cause the disruption of blood cells. A protein-denaturing solution is added to the mixture, and the resulting mixture is fully agitated to denature a protein contained in the sample, thereby forming an aggregate. The solution is centrifuged to leave the aggregate on the filter instrument (302) side, and the filtrate is supplied to the solid phase extracting agent through a filter unit (305) without collecting the filtrate. A necessary amount of a washing solution is added to the solid phase extraction instrument (303), the resulting mixture is agitated and centrifuged, and a supernatant is discarded. A necessary amount of an eluting solution is added to the solid phase extraction instrument (303), the resulting mixture is fully agitated and centrifuged, and a supernatant is discarded.