This study analyzes how the relationship between corporate income tax and employment varies according to the bargaining power of labor unions. To this end, we use a dynamic general equilibrium model to examine corporate income tax and the bargaining power of labor unions based on a span-of-control model. Previous studies on the relationship between corporate income tax and employment are inconclusive and do not examine the role of the bargaining power of labor unions in this relationship. Calibrated results obtained using data from Korea show that a reduction in only the corporate income tax rate slightly decreases total employment, but a reduction in the corporate income tax rate accompanied by a decline in the bargaining power of labor unions significantly increases total employment.