Method for producing drug substance-containing core, drug substance-containing core, pharmaceutical composition, and orally disintegrating tablet

Provided are: a method for producing a drug substance-containing core with an average particle size of 100 to 500 μm, the method comprising granulating by intermittently or continuously charging a drug substance powder into a fluid bed granulator while intermittently or continuously charging a coupling liquid into the fluid bed granulator with the contents of the fluid bed granulator flowing; a drug substance-containing core; a pharmaceutical composition; and an orally disintegrating tablet.