Generally, the chassis of an indoor RAC is composed of a rear-guider and a stabilizer. The aerodynamic performance of a cross-flow fan is strongly influenced by the various design factors of the chassis of an indoor RAC. The purpose of this paper is to select the optimum design factors through the aerodynamic performance of a cross-flow fan. The design factors are the leading angle of a rear-guider (${ heta}_1$), a stabilizer setup angle(${ heta}_2$), a rear-guider clearance(${epsilon}_1$), and a stabilizer clearance(${epsilon}_2$), respectively. As a result, the optimum design factors of an indoor RAC can be presented as a combination of ${ heta}_1=33^{circ}$, ${ heta}_2=55^{circ}$, ${epsilon}_1=6{sim}8mm$, and ${epsilon}_2=7mm$ through the analysis of a static pressure coefficient and a static pressure efficiency.