WATER TREATMENT DEVICE AND WATER TREATMENT METHOD

This water treatment apparatus is provided with: a ground electrode (2) extending in an axial direction; a high voltage electrode (5) coaxially arranged so as to surround the grounding electrode (2) from the outside in a radial direction; a dielectric (1) forming an annular gap with the ground electrode (2) and causing to generate a dielectric barrier discharge; a water-film forming portion (7) forming an annular flow path (7c) on one end side in an axial direction with an opening toward the annular gap at a narrower spacing than the annular gap along a circumferential direction between the water-film forming portion and the grand electrode (2), and causing water to be treated (90) to flow down toward the other end side as a water film (91) covering the grand electrode (2) when the one end side is directed upward to set the axial direction to be vertical.