The central regions of OB Associations are suitable for the study of the initial mass function since the constituent stars have not had sufficient time to migrate far from their formation site or to evolve from the main sequence. This paper reports on CCD observations of the central 7' x 7' region of the OB cluster Ocl 352, located in the H ii region IC 1805, that is within the association Cas 0B6, which is in turn part of the molecular cloud W4. Colors were determined for 160 stars in IC 1805 and this information allowed the initial mass function for the region to be determined. A weighted linear least-squares fit to this mass function in the mass range 2.5-30 Msun, yields a slope of Γ=-1.38±0.19. This is similar to the slope (-1.2S±0.17) determined using the brighter stars identified in a larger region (50' x50') of IC 1805 by Joshi & Sagar [JRASC, 77, 40 (1983)]. It is also close to the slope of the IMF determined by other modern studies of select OB clusters. A roll off in the number of low-mass stars is observed but this is attributed to incompleteness in this study's inventory of stars of mass less than 2.5 Msun.