Bitcoin, the most representative cryptocurrency, and the KOSDAQ150 index have a higher proportion of individual investors than the other financial products. As they present great investment opportunities, both are found to be highly volatile as well as high-risk financial products. Based on the correlation between the two products, this study proposes a more stable and a higher rate of return trading model for trading the KOSDAQ150 index alongside Bitcoin, enabling the investors to make sound and stable investments. The study utilizes the rough set theory for the development of the investment strategy. In conclusion, it was possible to achieve higher rates of return when trading the KOSDAQ150 index and Bitcoin together than when trading Bitcoin alone. The study demonstrates how the trading of Bitcoin allows for a long-term and a stable investment.