Production method for multicore optical fiber

A production method for a multicore optical fiber comprising in order:

• a preform forming step of forming a common cladding tube made of quartz glass and having a plurality of holes extending in an axial direction between a first end and a second end;
• an insertion step of inserting core rods formed of quartz glass in the plurality of holes of the common cladding tube in a state in which end portions of the core rods are recessed from the first end;
• a heat shrinkage step of reducing a diameter of the first end by heating the first end,
• a sealing step of sealing the plurality of holes by connecting a glass block to the first end;
• and
• a drawing step of producing the multicore optical fiber by depressurizing insides of the plurality of holes in the common cladding tube from the second end and performing spinning from the first end while combining the common cladding tube and the core rods.