To produce an inorganic fiber sheet having good breathability suitable for a separator in annealing and capable of being reclaimed, by wet papermaking of a dispersion liquid comprising an inorganic fiber, its by-product, i.e., shorts (having a specific ratio of the major axis to the minor axis), inorganic powder and an organic fiber.

This inorganic fiber sheet having the weight/unit area of 30-200 g/m2 (pref. 50-150 g/m2), (B) shorts which is the by product of the inorganic fiber, has the ratio of the major axis to the minor axis of 1-20 in a projected state and is held in the inorganic fiber in the ratio of the fiber to the shorts of (95:5)-(30:70), pref. (90:10) (50:50), (C) inorganic powder such as titanium oxide and (D) 2-20 wt.% (pref. 3-10 wt.%) organic fiber (e.g. kraft pulp) in water and then by adding a cationic flocculant to the dispersion to form flocculate, followed by diluting the flocculate to the solid content of 0.01-2 wt.% and by conducting wet papermaking.