The man, who had obesity, hyperlipidemia and other diseases, received a Sinovac jab on March 7. He lost consciousness at work on Saturday morning, about three weeks later.
He was declared dead after being rushed to hospital, with a preliminary diagnosis pointing to a sudden cardiac arrest.
Officials said the man did not report any discomfort after getting the jab at the vaccination centre in Kowloon Bay.
The case will be forwarded to government experts to investigate whether his death has any connection with the vaccination.
The man is the twelfth person to die after inoculation, with two of the cases after the BioNtech jab and others after the Sinovac.
Authorities said previous deaths were probably caused by pre-existing health conditions, instead of the jabs.