Finer calculation elements (meshes) are required to conduct an accurate solidification simulation for castings with thin sections. Calculation methods using non-structural meshes can keep its efficiency even for complex shaped castings, because the methods can use adaptive mesh size for parts with various size and regions around interfaces. However, methods using non-structural mesh tend to have difficulty in mesh generation and complexed calculation program. In this study, we conducted heat transfer and solidification simulation using an adaptive resolution particle method (ARPM), which uses various kind of element size as adaptive resolution method with simple calculation program similar to the method using structural meshes. As a result, the ARPM showed good accuracy of solidification simulation and improve its efficiency of the computational time and the memory usage, slightly reducing an energy conservation quality.