The ionic conduction of zeolite powder in ion-exchanged water and various other solutions was investigated. H-BEA-92.5, which contained many silanol groups, showed the highest conductivity of 1.1 x 10(-1) S cm(-1) at 95 degrees C in a 10,000 ppm NaCl aqueous solution. After controlling the amount of surface silanol groups by calcination or dealumination, zeolites with a relatively large number of surface silanol groups showed the highest conductivity in water. The improvement of conductivity with zeolite in water was also observed for zeolite-related materials with surface silanol groups. Therefore, we conclude that surface silanol groups play an important role in increasing the conductivity of solution with zeolite in water. Furthermore, it was revealed that the mechanism of conduction was similar to the Grotthuss mechanism because of its apparent activation energy.