A pressure equalizing structure that includes: a gasification furnace (3) for gasifying a carbon-containing fuel; a pressure vessel (5) housing the gasification furnace (3); an annulus section (7) filled with an inert gas and provided between the gasification furnace (3) and the pressure vessel (5). A pressure equalizing part (13), which is connected to the gasification furnace (3) to communicate between the inside of the gasification furnace (3) and the inside of the annulus section (7), is provided in a region where the in-furnace gas temperature inside the gasification furnace (3) is higher than the annulus temperature inside the annulus section (7).