To prevent a gate electrode exposed to a surface from making continuity with a reference electrode via a sample solution in electrolyte due to the nonuniformity of the combination density of a probe DNA that is combined on the gate electrode.

The sensor cell comprises: a metal fine particle (20) for combining with the probe DNA (30) selectively reacting with a target DNA on a surface; an electric field transistor Tr2 where a number of metal fine particles (20) are combined on a gate insulating film (25); and the reference electrode (21) that becomes a potential reference. Due to the hybridization of the target DNA and the probe DNA (30), the mutual conductance of the field effect transistor Tr2 is changed due to a change in a minute capacity formed between each metal fine particle (20) and the reference electrode (21), thus changing a current value outputted from a current output terminal in the field effect transistor Tr2.