Zeta potential measurement method and measurement device

A zeta potential measurement device for measuring a zeta potential of a sample surface using a relationship between an external pressure and a streaming potential, the device comprising:

• a pressure adjustment unit that changes the external pressure in a step-wise manner;
• a sample cell configured to contain a sample and a solution and to receive the external pressure;
• and
• a zeta potential calculation unit that sets a pressure change profile that has a rising part or a falling part which is of a shorter time than a relaxation time τ required for a responsive change in the streaming potential accompanying the change in external pressure, and a steady part in which pressure is held at a steady state for a time longer than the relaxation time τ, and calculates the zeta potential using at least four zeta potential measurement points and an asymptotic value of the streaming potential extrapolated from a transient response of the streaming potential occurring from the pressure change profile.