The purpose of this research is to analize calculation the cost of inpatient room, to compare between the conventional method and Activity Based Costing System. RSUD Kota Semarang has clasificated the costs based on something that financed, there are direct and indirect costs and used just a cost driver. Calculations using conventional methods for class III Yudistira’s Room is Rp 60.298, class II Bima’s Room is Rp 79.358, class IA Arimbi’s Room is Rp 152.688, class IB Banowati’s Room is Rp 200.849, and VIP class Brotojoyo’s Room is Rp 459.742. While the results of calculations by using Activity Based Costing System for class III Yudistira’s Room is Rp 73.485, class II Bima’s Room is Rp 95.316, class IA Arimbi’s Room is Rp 121.810, class IB Banowati’s Room is Rp 122.385 and VIP class Brotojoyo’s Room is Rp 218.087. The different on Yudistira’s Room is Rp 13.187 and Bima’s Room is Rp 16.042, calculation Activity Based Costing System causes the cost of inpatient room are more expensive than the conventional method. Then for the difference cost Arimbi’s Room is Rp (30.784), Banowati’s Room is Rp (78.464), and VIP Brotojoyo’s Room is Rp Rp (241.655) calculation Activity Based Costing System causes the cost of inpatient room become cheaper than conventional method. This difference is due to on conventional methods has distortion costs, because the consumption of resources on each activity is not same and used just a cost driver. While the method of Activity Based Costing, costs charged to product based on activities and resources that consumed by the product and also use more than one cost driver. Keywords: Analysis