Provided are elliptical, needle-shaped, or rod-shaped crosslinked polymer particles in which 5-100 mol % of all repeating units are repeating units derived from an unsaturated monomer having a functional group selected from an epoxy group, a carboxyl group, an amide group, a hydroxy group an amino group, and a thiol group, wherein (1) the average (LAV) length (L) in a two-dimensional projection diagram obtained by irradiating the particles with light from a direction orthogonal to the longitudinal direction is 0.1-80 μm, (2) the average (DAV) breadth (D) in the two-dimensional projection diagram obtained by irradiating, the particles with light from the direction orthogonal to the longitudinal direction is 0.05-40 μm, and (3) the average (PAV) aspect ratio (L/D) calculated from the length (L) and the breadth (D) is 1.5-30.
