To provide a simple liquid modifying apparatus preferable for especially modifying water containing radioactive substance, water containing potassium permanganate and a liquid containing polybiphenyl chloride.

The liquid modifying apparatus includes a plate material 15, a plate material 16 arranged so as to be opposed to the plate material 15, a plate material attaching member to which one end part of the plate material 15 and one end part of the plate material 16 are fixed, a liquid modifying container cover part 10a, a liquid modifying container 10 having the liquid modifying container cover part 10a, a liquid modifying container bottom part 10b and a liquid modifying container side part 10c, a water supply pipe 11 having opening parts 11b and 11c for ejecting a liquid to the other end part of the plate material 15 and the other end part of the plate material 16 and a drain pipe 12 for draining the liquid held to the liquid modifying container 10. The ratio of the inherent resonance frequency of the plate material 15 and that of the plate material 16 is set to 1.5-3.