To provide a method for removing a halogen series gas, which has high capability of treating a halogen series gas, can prevent ignition of an adsorbing agent, is free from formation of carbon dioxide and can reduce generation of wastes, and a removing agent to be used for the method. The method for removing a halogen series gas comprises bringing a gas comprising at least one halogen series gas selected from the group consisting of F 2 , Cl 2 , Br 2 , I 2 and a compound which undergoes hydrolysis to form a hydrogen halide or hypohalogenous acid into contact with a granulated product comprising from 80 to 99.9 mass% of an alkali metal base and from 0.1 to 20 mass% of a thiosulfate based on the total mass of the granulated product, in the presence of water, to remove the halogen series gas.