There is provided a sensor system and a sensor system using method which improve operability of a placing operation of placing a sensor in a living body and improve user-friendliness of users.The sensor system 100 has: a sensor member 110 which has the sensor which detects analyte components of the living body and transmits a signal, and a retaining portion which retains the sensor a needle assembly 210 which is detachably attached to the sensor member 110 and which has a guide needle which guides insertion of the sensor to the living body a signal processing circuit member 310 which is detachably attached to the sensor member, and which has an electronic circuit which processes the signal from the sensor and a fixing member which fixes the sensor member to a skin of the living body, and the sensor is placed in the living body in a state in which the signal processing circuit member is attached to the sensor member.
