To provide a reciprocation movement platform seat of a conductivity detector for enabling anyone to easily confirm installation positions of the conductivity detector in a state that a detection section is inserted into a chip of a meter main valve while a sample is measured and in a state that the detection section is extracted to a position in which it is not clamped by the meter main valve while the sample is not measured.

The reciprocation movement platform seat includes: a screwed rod 7 rotated by an operation of an operation handle; a movement base platform 8 mounted to the screwed rod 7 in a state that the conductivity detector 1 is attached, and moved in the longitudinal direction of the screwed rod 7 by a rotation of the screwed rod 7; and a limiting section 11 for limiting a movement distance in the longitudinal direction. When the movement base platform 8 reaches the installation position of the conductivity detector 1 in a state that the detection section 5 of the conductivity detector 1 is inserted into the chip of the meter main valve G while the sample is measured, or when the movement base platform 8 reaches the installation position of the conductivity detector 1 in a state that the detection section 5 is extracted to a position in which the detection section 5 is not clamped by the meter main valve G while the sample is not measured, the limiting section 11 stops the rotation of the screwed rod 7, and limits a movement range of the movement base platform 8.