Bank of Japan Gov. Haruhiko Kuroda's policies have a surprise new critic: the head of Japan's stock exchange.

The central bank's purchases of exchange-traded funds are distorting the market, Japan Exchange Group Inc. CEO Akira Kiyota said. Kuroda's program of spending ¥6 trillion a year on the funds artificially depresses volatility, which keeps people from trading, said Kiyota, who was previously more supportive of the policy.

"It's not good in the long run," Kiyota said during an interview in Tokyo last week. "If you keep buying ¥6 trillion a year, that means constant distortion."