Sony Computer Entertainment in Tokyo said Monday the problem lasted two hours but has been fixed globally. It said the cause is under investigation, but there is no sign of any material being stolen.
Last week, the computer systems of Sony Pictures Entertainment were disrupted by a cyberattack and confidential information including unreleased movies was leaked on the Internet.
North Korea was among the suspects, but it has denied responsibility.
The FBI is investigating threatening emails sent to some employees of Sony Pictures Entertainment, and trying to identify the person or group responsible.
There was no indication of a link between the PlayStation and Sony Pictures incidents.
A hacker group calling itself Lizard Squad appeared to take responsibility for the attack on its Twitter account, tweeting "PSN Login #offline."
Earlier this year, Lizard Squad warned that explosives might be on a flight that included a Sony executive among its passengers, and claimed responsibility for a disruption to the PlayStation network. American Airlines diverted the domestic U.S. flight to a nearby airport.
In that incident, hackers orchestrated a so-called denial-of-service attack against Sony, which involved overwhelming the company's game network with fake visits so that legitimate users couldn't get through.
In 2011, hackers compromised the company's network including the personal data of 77 million user accounts. Since then, the company has repeatedly said its computer security has been upgraded.
Yuri Kageyama on Twitter: https://twitter.com/yurikageyama