To provide a resin composition and a dispersant using it which is a component useful for long-term stability of homogeneous dispersion of particles.

The resin composition contains a copolymer having the following characteristics ()-(): () the polymer includes a monomer (A) having an amino group and a monomer (B) except the monomer (A); () the overall light transmittance in a 5% solution is 95% or more and transmittance at 500 nm is 95% or more; and () a molecular weight distribution is 1.0-2.0.