The dry-type photochlorination of poly(vinyl chloride) (PVC) was carried out by using a rotary vessel reactor and a fluidized bed reactor in order to obtain useful information for designing and industrializing a dry-type photoreactor. The results of the reaction rate analysis showed that the chlorination reaction rate could be expressed by an overall rate equation of 1st order with respect to the concentration of poly(vinyl chloride) and of 0.5-order with respect to the concentration of chlorine gas. The overall reaction rate constant K [1/min] followed the Arrhenius equation. K was also strongly correlated with the irradiated ultraviolet power per mole of PVC charged in the reaction vessel, I [mW/mol]. Furthermore, K was affected by the mixture conditions of the powder (number of rotations in the rotating vessel reactor). Hence, an optimal dry-type photoreactor can be designed by further clarifying the relationship between the overall reaction rate constant and the reaction conditions and mixture conditions.