PURPOSE: To obtain the subject carbon fiber giving a polyacetal resin composite material having a specific volume resistivity and high tensile strength by treating a carbon fiber with a solution containing a mercaptosilane and an epoxy resin.

CONSTITUTION: A carbon fiber is treated with a solution containing a mercaptosilane and an epoxy resin and dried to obtain a carbon fiber holding 1-15wt.% of the above mixture. The treated carbon fiber is compounded to a polyacetal resin in an amount of about 20wt.% to obtain a composite material having improved abrasion resistance and tensile strength. The obtained composite material has a volume resistivity of 105 to 108Ω.cm, exhibits excellent characteristics as a composite material and is suitable as a material for preventing electrostatic hazard.