This trend really worries me: Cramer

Cramer: This IPO 'not expensive'

The deluge of initial public offerings that captured investors' attention last week, as well as the string of red-hot IPOs in the days to come, will likely put downward pressure on the stock market this week, Jim Cramer said Monday on CNBC.

(Read more: Put these IPOs on your radar: Pro)

What's the problem? Companies that held IPOs recently saw shares spike while rival companies that may have gone public a year ago or more only fell, Cramer suggested.

Shares of existing cloud computing service providers, for example, "were getting killed" last week while rival companies that held IPOs "spurred up," Cramer said. The same was true of several other sectors, too, he noted.

(Read more: IPOs swamp market, swim against 'bubble' tide)

"Senior biotech companies were annihilated last week, but not the new IPOs. That's not tenable. Something has to give and give this week," Cramer said on "Squawk on the Street." "You can't keep having the second-tier IPOs do much better than the first-year, existing companies."

Five companies went public on Friday. A10 Networks, Amber Road and TPG Specialty Lending debuted on the New York Stock Exchange while Versartis and Borderfree launched on the Nasdaq. Some of these companies might be worth investing in, but Cramer said most are largely inferior to their rivals that have been around longer.

"We've got way too many IPOs ... last week, the IPOs were so thick that you could not keep track of the Amber Roads and the Paylocitys. In the meantime, was down 11 straight points," he said. "Let's be aware: You can't have two markets. A house divided will not stand."

Meantime, 10 companies will go public this week, including King Digital, maker of mobile game "Candy Crush," and food delivery website Grubhub.

(Read more: Grubhub's IPO could value firm at $1.72 billion)

—By CNBC's Drew Sandholm. Follow him on Twitter @DrewSandholm.