We present evidence that fund managers inflate period-end portfolio prices with last-day purchases of stocks already held. We find that institutional investor tends to abnormally trade stock with opaque information stock, trading of which is not related to fundamental value of the stock and tends due to institutional investor increase selling more on looser portfolio and decrease selling on winner portfolio near the period-end. This study provides the issue that building market mechanism is more important than increasing the market dominance of institutional investor.