For the machining of elastomer, the mold tool is usually employed. However, fabrication of the mold tool is expensive and time-consuming process. So, the method is unsuitable for small lot production. Elastomer machining by endmilling can be an effective approach because of its flexibility. The objective of the research is to realize a high-precision elastomer machining in small lot production. At the milling of elastomer, there are two issues to be tackled. One is to reduce the deformation of the workpiece, the other is to control the appropriate surface generation. For the first issue, a concept of adaptive workpiece fixturing is employed to enhance the workpiece rigidity. A model based operation planning is proposed to overcome the second issue. Dedicated support tools for each machining step can help to control the deformation. Rapid prototyping technology enables to realize the fabrication of dedicated support tools. An experimental result of elastomer machining is also described in this paper. The result shows the proposed method is a promising approach.