Efrata Motor Automobile Repair Shop is one of the Automobile Repair Shops that operates on Bekasi area that provides spare parts replacement. Efrata Motor Automobile Repair Shop business operations including inventory and car spare parts sales transaction. Until now, all inventory and sales transaction activity still using filing system. Over time, Efrata Motor Automobile Repair Shop undergo a rapid development, so the filing system seems less effective and efficient. Therefore, a new system based on information technology was made that will be used as operational system for inventory and sales activity on Efrata Motor Automobile Repair Shop. This application developed using prototyping methodology. Application created using Microsoft Visual Studio 2008 and Microsoft SQL Server 2005. Application designed with UML modeling version 2.0. Once application design is completed, than tested by using black-box testing and scenario testing. Result of this paper is an application to support inventory and sales activity on Efrata Motor Automobile Repair Shop. This application provides several features for head of admin, owner, cashier, ware house staff, purchasing supervisor or purchasing department, and head of finance or finance department to manage customer data, car data, determine purchasing amount, determine minimum stock quantity, input purchase order data, input incoming goods, manage suppliers, manage goods master data, determine sales price, and do transactions that related to sales and inventory activity.