The present invention relates to an opening/closing hinge construction for an electronic and electrical equipment housing. By improving the hinge construction so that the hinge construction between a body case and body cover is contained within the housing, the housing is prevented from being large-sized and the assembling property is enhanced, whereby the whole manufacturing cost including the assembly cost is reduced. The construction is such as to open and close the body case forming an equipment housing by the body cover of cover member, and a hinge sheet having flexibility formed into a sheet form is used for a hinge connection portion. One end of the hinge sheet is fixed to the interior of the body case by using hinge bosses and set screws as a fixed locking end, and the other end is fixed to the inside of the body cover as a movable locking end. At the movable locking end, two elongated hinge variable adjusting grooves extending in the direction in which the movable locking end is connected to the fixed locking end in the body case are formed in parallel. The hinge sheet is locked at an arbitrary position in the hinge variable adjusting groove via a hinge fixing plate by means of set screws.