We investigated whether the increase in the US shale gas production changed the structures of the US and Japanese natural gas markets using market data for the period 2002:5-2012:5. Our analysis consists of a structural break test and market integration analysis. The Bai and Perron structural break test detected a break point of natural gas prices and consumption in 2005 as well as other external shocks Hurricane Katrina and the Lehman Shock - that are irrelevant to shale gas development. We eliminated the impact of these shocks by separating the data set using the breaks identified in our analysis. We found the breaks skewed the estimation; a market linkage existed between the US and Japanese markets in the original data set, while it did not in the separated data. The vector autoregressive (VAR) model also indicated a significant change before and after the break point; the US market had a one-side influence on the Japanese market before 2005, but the influence disappeared after 2005. Our results implied that the shale gas revolution, triggered by the increase in shale gas production in 2005, caused the change in the relationship between the US and Japanese natural gas markets. (C) 2013 Elsevier Ltd. All rights reserved.