To obtain a binder for glass fiber which prevents fluffing caused by breaking of single glass fiber and enhances weaving efficiency of air-jet weaving machine.

This binder for glass fiber comprises starch as the main film forming agent, a smoother made by emulsifying a smoothing component containing paraffins and a fatty acid triglyceride with an emulsifier, and a cationic softener, wherein starch is 15 to 25 times by weight of the effective component of the cationic softener on solid base, and as the emulsifier, a polyoxyechylene sorbitan monostearate with 13 to 16 HLB and a polyethylene glycol monooleate with 9 to 13 HLB are used together. A glass fiber which has the above binder adhered thereon is also provided.