A concentration meter is a concentration meter that measures a concentration of a predetermined solution, and includes: a main body section including an opening portion, and an internal liquid and an electrode that are housed in the opening portion; a permeation membrane that seals the opening portion; a water-holding section that is opposed to the permeation membrane; and an inflow/outflow section which is an opening that allows a clearance between the permeation membrane and the water-holding section to communicate with an outside space of the main body section, wherein the permeation membrane and the water-holding section are separated from each other by a distance in which the solution is held in the air due to a surface tension of the solution, with the solution contacting the permeation membrane and the water-holding section.