In recent times, economy and environmental safety have become very important factors in the construction of soil structures. Floating-type deep mixing soil stabilization has the advantage of reducing the cost of construction of soil structures on deep soft soil layers. Therefore, it is important to elucidate the mechanism of the consolidation settlement of improved ground with floating columns. First, in order to investigate the effects of the improvement ratio, improvement depth, and arrangement of columns, one-dimensional consolidation tests were carried out on a model ground with floating columns. The results of the tests were then compared with those obtained using a settlement model based on the homogenization method with a consideration of the stress distribution ratio. Finally, loading model tests were conducted under a plane strain condition to simulate the consolidation deformation of the improved ground. Under these test conditions, it was confirmed that the settlement of the improved portion can be estimated by using the proposed model.