A liquid developer set formed of a liquid developer used for developing an electrostatic latent image and containing a carrier liquid, a charge director and toner, a first liquid, which is obtained by removing a solid component from the liquid developer, having a charge director concentration C1 and a conductivity E1; a concentrated liquid developer containing the carrier liquid, the charge director and the toner in a higher concentration than the toner concentration of the liquid developer, a second liquid, which is obtained by removing a solid component from the concentrated liquid developer, having a charge director concentration C2 and a conductivity E2 substantially equal to the concentration C1 and the conductivity E1, respectively; and a diluent containing the carrier liquid and the charge director, and having a charge director concentration C3 and a conductivity E3 substantially equal to the concentration C1 and the conductivity E1, respectively. The concentrated liquid developer, the diluent and a method of manufacturing the diluent.