Agent-based simulation is one of promising approaches to understand and design complex socio-economic systems. The U-Mart project is a research program of providing economists and computer scientists with an artificial market, an agent-based simulation system of a financial market, as a test bed for interdisciplinary study. The U-Mart system is a set of artificial market software developed by the U-Mart project. It contains network-based and stand-alone artificial market servers, GUI-based human interfaces for manual trading in the market and monitoring of the market, API and a wrapper program for development of software agents, and a log viewer for analysis of experimental results. This paper gives an over-view of the U-Mart project/system. Concept of a revised version of the U-Mart system under development is also discussed.