Excess supply of office space caused the so called 2003 shock in real estate market for offices. This shock became a social issue due to its structural effect to real estate market. One of fundamental factor is the lack of information on other development projects, and thereby misleads developers' decision making. One remedy for this is to set up a development information system that publicizes all the approved projects comprehensively to assist developers for appropriate decision making. A related issue is the need for planning measure to ensure improvement of urban environment in the future.To enable it, tax and property right system as well as development regulation should be amended so that cooperative projects and conversion projects are promoted.