Method for producing porous glass fine particle body and method for producing optical fiber preform

A method for producing a porous glass fine particle body, the method comprising:

• a first layer formation step of continuously forming a first soot layer having a thickness of no more than 1.0 mm by no more than one burner among a plurality of burners in a burner group, wherein
• the first soot layer is formed on a surface of a rotating starting base material without a break in a longitudinal direction of the rotating starting base material;
• and
• an outer layer formation step of forming outer soot layers on an outside of the first soot layer while:
• supplying a raw material gas to each of the burners in the burner group, and
• moving the burner group in a reciprocating manner in the longitudinal direction relative to the rotating starting base material, and/or moving the rotating starting base material in a reciprocating manner in the longitudinal direction relative to the burner group, wherein
• one of the outer soot layers is a second soot layer formed on the first soot layer by the burners in the burner group,
• wherein the burner group and the rotating starting base material move relatively to each other along the longitudinal direction,
• the outer soot layers have boundary surfaces formed at longitudinal intervals that longitudinally divide deposited soot layers formed by different ones of the burners in the burner group, and a number of the boundary surfaces formed in the outer layer formation step is N-1, where N is a number of the burners in the burner group.