Real estate market is regarded as inefficient and the belief provides grounds for the arguments on price bubble and government regulation. Most empirical analyses on the housing market in Korea support the belief as well. This study conducts an analysis on the efficiency of the office market in Seoul through two tests using random walk model and dividend discount model, respectively. The empirical result suggests that through the random walk model the market turned out to be inefficient as the return of office could be explained by ARIMA model, while the efficiency was accepted in the dividend discount model as the capitalization rate could be explained by ‘ex-post’ return and NOI growth rate. From the point of view that how fully and immediately the price reflects the information is critical for the market efficiency, this result does not support the efficiency of the market. The poor efficiency, however, could not be an ample evidence of price bubble. Because price bubble used to be based on the absence of investors’ rationality as well.