We synthesized graft compolymers composed of water soluble chitosan (WSC) and poly(ethylene gycol) (abbreviated as WSCP) to prepare core-shell type nanoparticles based on polyelectrolyte complexes between WSC backbone and anionic drug. Nanoparticulate polyelectrolyte complexes were formed through ultrasonication. WSCP were used to form core-shell type nanoparticles with WSCP and atRA and showed ability to form spherical nanoparticles. Particle sizes of WSCP-drug polyelectrolyte complexes was 50 - 800 nm according to the preparation condition. Loading efficiency of drug into chitosan polyelectrolyte complexes was over 60 ％ (w/w) at all of the formulation. This drug loading efficiency was higher than other types of drug carriers such as liposomes, conventional nanoparticles, and lipid nanoparticles.