Provided is a method of manufacturing a porous glass deposition body for optical fiber comprising depositing silica powder on a starting member being raised and rotated by using burners with different deposition positions. With a glass raw material flow rate supplied to a core deposition burner represented by F.sub.1 and a total flow rate of glass raw material supplied to a cladding deposition burner adjacent to the core deposition burner represented by F.sub.2, during an initial deposition stage occurring before gas conditions reach a stable state, glass raw material is supplied to points at the same longitudinal position of the deposition body such that a glass raw material flow rate ratio F.sub.2/F.sub.1 is no less than 0.69 and no greater than 1.03.

A method for manufacturing a glass ingot includes preparing a supply system including a gasifier that gasifies a raw material compound and a burner that combusts the gasified raw material compound; adding an oxygen-containing gas to the raw material compound at a plurality of addition places including an upstream addition place located in the gasifier or on an upstream side of the gasifier and a downstream addition place located on a downstream side of the gasifier in which locations of the raw material compound in a flow direction are different in the supply system so as to form a raw material mixture; and adding the oxygen-containing gas at the upstream addition place so that a concentration of oxygen or a concentration of the raw material compound in the raw material mixture is not in a combustible range of the raw material mixture.

A method for manufacturing a glass ingot includes preparing a supply system including a gasifier that gasifies a raw material compound and a burner that combusts the gasified raw material compound; adding an oxygen-containing gas to the raw material compound at a plurality of addition places including an upstream addition place located in the gasifier or on an upstream side of the gasifier and a downstream addition place located on a downstream side of the gasifier in which locations of the raw material compound in a flow direction are different in the supply system so as to form a raw material mixture; and adding the oxygen-containing gas at the upstream addition place so that a concentration of oxygen or a concentration of the raw material compound in the raw material mixture is not in a combustible range of the raw material mixture.

A method for manufacturing an SiO.sub.2TiO.sub.2 based glass upon a target by a direct method, includes: an ingot growing step of growing an SiO.sub.2TiO.sub.2 based glass ingot having a predetermined length on the target by flame hydrolysis by feeding a silicon compound and a titanium compound into an oxyhydrogen flame, wherein the ingot growing step includes: a first step of increasing a ratio of a feed rate of the titanium compound to a feed rate of the silicon compound as the SiO.sub.2TiO.sub.2 based glass ingot grows until the ratio reaches a predetermined value; and a second step of gradually growing the SiO.sub.2TiO.sub.2 based glass ingot after the ratio has reached the predetermined value in the first stage with keeping the ratio within a predetermined range.