PURPOSE: To improve the permeability of oil and to lengthen the life by using porous hollow glass as an inorganic additive of friction material obtained by forming mixed material comprising a friction condition, an inorganic additive and resin.

CONSTITUTION: Mixed material comprising base material, a friction conditioner, an inorganic additive and resin is formed to manufacture wet type friction material. Porous hollow glass is used as at least a part of the inorganic additive. The porous hollow glass has a particle diameter of 10W100μm and a pore-size of 0.1W5μm, and its addition proportion by weight is 20W60 wt% per 100 wt% the whole of components except a resin component. Thus retention of oil is improved, a cooling effect and a lubricating effect produced by oil of friction material are enhanced, so that durability and heat resistance can be improved, a friction coefficient can be stabilized over a long period of time, and abrasion loss can be lowered so as to lengthen the life.