A gas reaction apparatus for manufacturing base material of optical fiber and a multi-wall pipe type burner for the gas reaction apparatus. The gas reaction apparatus includes a mechanism which heats or heat insulates at least one of gas passages of the burner for gaseous raw material of optical fiber so as to set a saturated vapor pressure of whole kinds of the gaseous raw material higher than a partial pressure of raw material of optical fiber in the gaseous raw material when the gaseous raw material is fed through the one of the gas passages.