An object of the present invention is to provide an electrodeposition paint composition and a method of forming an electrodeposited coating, which exhibit quality of coating deposition even in the interior of narrow spaces of objects subjected to painting. A solution of the object is cationic electrodeposition paint composition in which in an aqueous medium contained are a cationic epoxy resin, a blocked isocyanate curing agent, a hydrophobic agent wherein an SP value of the hydrophobic agent (C) is 10.2 or more and less than 10.6 and is lower by 0.6 to 1.0 than an SP value of the cationic epoxy resin, a viscosity modifier, and a neutralizing acid, and in which coulombic efficiency of the cationic electrodeposition paint composition is 2.0 to 2.5 mg/(μm·C). A voltage boost rate of the voltage in painting is 30 to 70V/10 seconds.