A producing method of resin particles, which comprises at least an emulsification step of emulsifying a composition containing at least a polymerizable
monomer and a
polymerization step to form droplets of the composition, and a
polymerization step of polymerizing the polymerizable
monomer in the droplets to synthesize resin particles, wherein the composition is one selected from Composition A,
Composition B, or
Composition C: (Composition A): a composition containing a vinyl-based
monomer,
lactone, a vinyl-based monomer
polymerization catalyst for polymerizing the vinyl-based monomer, and a
lactone polymerization catalyst for polymerizing the
lactone (
Composition B): a composition containing a
polyester resin, lactone, and a lactone catalyst for polymerizing the lactone (
Composition C): a composition containing a vinyl-based monomer, a cyclic keteneacetal compound represented by the following general formula (1), and a
radical polymerization initiator (in the general formula (1), R represents a chain or cyclic
divalent aliphatic group optionally containing an
ether linkage, and the aliphatic group may have a
substituent.)