In quality control of industrial products, it is very important that not only qualities of materials and parts, design, but also a manufacturing work accords to instruction manuals for manufacturing process. Generally, most assembly process such as assembly line and cell production system have processes in everywhere to confirm quality and work in former processes. However, there are some cases that are difficult to be confirmed in later processes. For example, to fix a part by some screws, it is desirable to drive in diagonal order little by little. However, it is not easy to detect in appearance in case of this desirable procedure is violated. Therefore, we are developing a system to improve quality of industrial products. This system deals manufacturing processes as context, and grasp manufacturing process, recognizes context by tracing motions of worker’s arm/hand by using terrestrial magnetism sensors and accelerometers. In this paper, as first step, we show that violation of desirable motion is distinguishable by dividing manufacturing process as context into some fundamental motion, and tracing motions by each context. Also, we discuss on fundamental conditions to introduce the system in actual manufacturing process.