Burner for synthesization

A burner for synthesization to synthesize glass particles that form a porous glass base material, the burner for synthesization comprising:

• a raw material gas injection portion to inject raw material gas in a direction toward a target;
• an inner injection portion to inject one of combustion assisting gas and combustible gas in a direction toward a first merging point;
• and
• an outer injection portion to inject the other of combustion assisting gas and combustible gas in a direction toward a second merging point that is positioned closer to the inner injection portion than the first merging point, wherein
• the injection direction of each of the inner injection portion and the outer injection portion is tilted toward the injection direction of the raw material gas injection portion,
• the outer injection portion is positioned further from the raw material gas injection portion than the inner injection portion and the injection direction of the outer injection portion is tilted more strongly toward the injection direction of the raw material gas injection portion than the injection direction of the inner injection portion,
• the first merging point is an intersection between an axis extending from the raw material gas injection portion in the injection direction thereof and an axis extending from the inner injection portion in the injection direction thereof, and
• the second merging point is an intersection between an axis extending from the inner injection portion in the injection direction thereof and an axis extending from the outer injection portion in the injection direction thereof.