The hack, which exposed the personal details of more than 77m customers including many in Australia has been described as one of the "most serious" breaches of the Data Protection Act the Commission has ever dealt with.
The regulator said Sony should have had better protections in place, given the amount of credit cards it had on file, and accused it of putting its trusting users at serious risk of identity theft.
David Smith, deputy commissioner and director of data protection at the ICO, said in a press statement: "There's no disguising that this is a business that should have known better. It is a company that trades on its technical expertise, and there's no doubt in my mind that they had access to both the technical knowledge and the resources to keep this information safe."
Sony to appeal
Sony said it would be appealing against the verdict and claimed it was still building more layers of defence against future accounts.
Sony executives added "Criminal attacks on electronic networks are a real and growing aspect of 21st century life and Sony continually works to strengthen our systems, building in multiple layers of defence and working to make our networks safe, secure and resilient.
"The reliability of our network services and the security of our consumers' information are of the utmost importance to us, and we are appreciative that our network services are used by even more people around the world today than at the time of the criminal attack."