In this paper, a new method based on idea of the polar coordinate system for fast database searching in Just-In-Time approach is proposed. Just-In-Time approach is a local modeling technique which builds a linear model using a database constructed by the input and output data. However, there is trade-off between number of data to be used and computational burden. As the quantity of database increases, Just-In-Time approach builds a more accurate linear model, however, the processing speed becomes slower. The proposed method searches database quickly with a lot of data and builds an accurate local linear model. Then, the proposed method is examined through numerical simulation of a trajectory tracking control of SICE-DD arm.