In order to reduce the lead-time and cost, the technology of rapid prototyping (RP) has been widely used. However, RP techniques have disadvantageous characteristics according to their working principles: a low building speed caused by a thin-layer, stair-stepped surface of a part due to layer-by-layer stacking with a vertical edge, an additional post-processing and high cost for installation, operation and maintenance of the RP apparatus. The objective of this study is to propose a new RP process, progressive-type variable lamination manufacturing using expandable polystyrene foam (VLM-SP), to overcome the disadvantageous characteristics and to develop an apparatus for the implementation of the process. The proposed RP system employs several novel techniques such as a thick layer with the thickness less than 2 mm, a sloped surface with the first-order approximation between the top and bottom surfaces of each layer, a building sequence that performed stacking and bonding after cutting, the concept of a unit shape part (USP) and an automated synchronized four-axis hot-wire cutting system. In this paper, the characteristics of the proposed process and apparatus are discussed. The experiments are carried out to verify the bonding strength of the bonded area. Several three-dimensional shapes are fabricated on the prototype of the VLM-SP apparatus in order to investigate the applicability of the proposed process. In addition, in order to examine the efficiency of the VLM-SP process, the prototypes of VLM-SP are compared with those of commercial RP processes [LOM (laminated object manufacturing) and FDM (fused deposition modelling)] from the viewpoint of geometrical conformity, building time, building cost and dimensional accuracy. As a result of the comparison, it has been shown that the proposed process is an efficient rapid prototyping process.