To provide a fireproof wall structure having a fire resisting function for one hour and attaining convenience of construction and improvement in strength, and to provide a method for constructing the fireproof wall structure.

The fireproof wall structure includes a plurality of fireproof panels 3 connected to steel members 1 of a structural skeleton through connecting members; external facing backing 5 anchored to the surfaces of the fireproof panels 3 and connected to the steel members 1; and flame-resisting external facing plates 7. The fireproof panel 3 includes a heat insulating layer 3a formed by solidifying an inorganic granular material; an intermediate layer 3b filled with an inorganic fiber body or an inorganic foam; and a base layer 3c of metal plate shape. The external facing backing 5 includes a backing part 5a for anchoring the flame-resisting external facing plate 7, a base part 5c and a rising part 5b. The connecting member includes a sealing part for covering a joint part of the fireproof panels 3; a filling part bent at a right angle on the back face of the sealing part to enter the joint part by less than half of the thickness of the fireproof panel; and an anchor part further bent at a right angle from the tip of the filling part and embedded in a joint face of one of the fireproof panels. The edge parts of the fireproof panels 3 forming a fitting part are clamped from the front and rear sides by the sealing parts of a pair of connecting members.