When we estimate office migration in particular area, the general method is spatial interaction model. The model can not describe change of number of offices in the target area, because the model is constructed without considering comings and goings to the outside and establishments and closings of offices. In this paper, we propose office migration model which can describe change of number of offices in the target area. We introduce outside zone to describe comings and goings to outside zone, establishments and closings of offices. Our model is based on a logit model. We adapt spatial interaction model and the model with outside zone to Tokyo and Yokohama, and compare these models by AIC. The result shows that the model with outside zone is superior to spatial interaction model in the case that number of offices in the target area is variable.
