A sample information obtaining apparatus includes an electromagnetic wave generator; a sample holding unit which holds a sample to be tested and serves as a polarizer having a polarization axis which defines how an incident electromagnetic wave is to be divided according to a polarization state of the incident electromagnetic wave; an electromagnetic wave detecting unit which separately detects a transmitted electromagnetic wave transmitted through the sample holding unit and a reflected electromagnetic wave reflected off the sample holding unit, the transmitted and reflected electromagnetic waves being obtained by dividing the incident electromagnetic wave incident on the sample holding unit according to a relative positional relationship between the polarization state of the incident electromagnetic wave and the polarization axis of the sample holding unit; and a processor which processes signals of the electromagnetic waves detected by the electromagnetic wave detecting unit and obtains information about the sample.