The recent stock market rallies have only the Federal Reserve's monetary policy to thank, DoubleLine Capital's Jeff Gundlach said Thursday on CNBC.
"I think everything kind of begins and ends with quantitative easing," he said. "It's really just at the centerpiece of everything, and it creates a demand for, obviously, Treasury bonds."
On "Fast Money," Gundlach said that the Fed has created some confusion for investors.
"It creates a low basis of comparison that is keeping the trend toward being anything with a yield on it as being successful investment that will continue to, I think, appreciate in value and lead to even more of a conundrum for investors in terms of what they're supposed to do going forward," he said.
But it can't last forever, Gundlach added.
"This trend's been in place for a couple of years. People have been fighting it," he said. "At some point, it's going to end, probably badly. But it's still going on. The Fed's not going to stop. We're probably about in the eighth inning, and it's going to contiunue to trend in the same direction, I think."
(Read More: Rally Not Yet in Ninth Inning: Pro)
Gundlach also responded to a comment from Berkshire Hathaway's Warren Buffet that U.S. Treasury bonds were a "terrible investment."
"Depends what your time frame is," he said. "Over the short-term, bonds are not terrible. Treasury bonds will be an OK to OK-minus investment, probably, for that time period … just as they've been an OK investment, or OK-minus investment, since we went into QE nonstop, which was the early part of October 2011."
Gundlach pointed to the Treasuries ETF, TLT, which had a 3½ percent annualized return.
"That's not great, but it's not bad," he said. "I think that's going to continue."