Provided is an epoxy resin composition containing an epoxy resin (A) and an epoxy resin curing agent (B), wherein the epoxy resin (A) contains from 10 to 65 mass % of an epoxy resin (A1) and from 35 to 90 mass % of an epoxy resin (A2), the epoxy resin (A1) having a glycidyloxy group derived from resorcinol, and the epoxy resin (A2) being other than the epoxy resin (A1) and containing an aromatic ring; the epoxy resin (A2) contains 70 mass % or more of an epoxy resin having a glycidyloxy group derived from bisphenol F; and a cured product of the epoxy resin composition has a hydrogen gas permeability coefficient of 6.410.sup.11 or less [cc.Math.cm/(cm.sup.2.Math.s.Math.cmHg)]. Also provided are a cured product of the epoxy resin composition, a fiber-reinforced composite material, and a high-pressure gas container containing the fiber-reinforced composite material.

A processing apparatus includes: a processing container configured to accommodate a substrate; a storage tank connected to the processing container via a gas supply pipe; a pressure sensor configured to detect a pressure in the storage tank; a valve provided in the gas supply pipe between the processing container and the storage tank; and a controller configured to control an opening degree of the valve based on the pressure in the storage tank detected by the pressure sensor. The controller is further configured to control the opening degree of the valve to make a drop amount of the pressure become equal to a set discharge pressure, the drop amount being calculated by subtracting the detection value of the pressure sensor in a state where the valve is opened, from the detection value of the pressure sensor before the valve is opened.