PURPOSE: To exchange a cell culture medium without losing the cells by measuring the concentration of glucose in a culture medium, controlling the concentration of the glucose to ≥a set value in response to the decreased amount of the glucose, determining an exchange time and an exchange solution volume, and reducing the necessary volume of the culture medium.

CONSTITUTION: This method for exchanging a culture medium containing glucose as an indicator comprises supplying the culture solution into a medium container 1 with a medium supply device 10, floating cells in a cell culture chamber 2, periodically measuring the glucose concentration of the culture solution with a glucose sensor 4 set in the medium container 1, determining such a culture solution supply volume as giving a higher value than a set value, obtained with an arithmetic means 5, when the concentration of the glucose is decreased to a lower value than the set value, supplying a fresh new culture solution into the medium container with a pump 6 from a culture solution tank 7 receiving the fresh medium, and flowing out a part of the culture solution received in the medium container 1 into a discharged solution tank 8 to reduce the necessary volume of the medium solution. Thus, the cell-cultured solution is efficiently exchanged, while preventing the consumption of the medium and maintaining the viability of all the cells without losing the cells when the medium is exchanged.