PROBLEM TO BE SOLVED: To provide an opening structure and a fine bubble generating device capable of preventing a lid from coming off when an internal pressure is applied, at an opening of a structure where an internal pressure is applied.SOLUTION: In the configuration of an opening structure according to the present invention, the opening structure where a cylindrical lid 230 covering a cylindrical opening 210a of a structure (body part 210) to which an internal pressure is applied is mounted to the opening 210a has: an L-shaped groove 214 consisting of a vertical groove 216a extending axially from an opening end of the opening and a horizontal groove 216b extending circumferentially and contiguously to the vertical groove on an outer peripheral surface 212 of the opening of the structure a claw 234 fitted into the L-shaped groove 214 on the inner peripheral surface 232 of the lid 230 and a protruding portion 220 for restricting the circumferential movement of the claw 234 when an internal pressure is applied to the structure, on at least one of the surface of the opening end side of the horizontal groove or the surface and the opening end side of the claw of the L-shaped groove.SELECTED DRAWING: Figure 4COPYRIGHT: (C)2018,JPO&INPIT【課題】内圧がかかる構造物の開口部において、内圧がかかっているときに蓋が外れてしまうことを防止することが可能な開口部構造および微細気泡発生装置を提供することを目的とする。【解決手段】本発明にかかる開口部構造の構成は、内圧がかかる構造物(本体部210)の円筒形の開口部210aに、開口部210aを覆う円筒形の蓋230が取り付けられる開口部構造において、構造物の開口部の外周面212には、開口部の開口端から軸方向に延びる縦溝216aと、縦溝に連続して円周方向に延びる横溝216bからなるL字溝214が備えられていて、蓋230の内周面232にはL字溝214に嵌る爪234が備えられていて、L字溝の横溝の開口端側の面、または爪の開口端側の面の少なくとも一方に、構造物に内圧がかかったときに爪234の円周方向の移動を規制する突起部220を有することを特徴とする。【選択図】 図4
