Chang Chih-chiang, 36, was convicted and sentenced on yesterday on charges of abandoning his mother, resulting in her death, the high court said. He can appeal the ruling.
The case came to light after Chang's wife contacted the police in August last year when she found her diabetic, bedridden mother-in-law dead in their apartment in northern Taiwan.
When officers arrived they discovered the body, which weighed less than 30 kilogrammes (66 pounds), infested with maggots in a room littered with trash.
Local media have reported that Chang liked to spend his time playing computer games at Internet cafe, and that he ignored his sick mother even though they lived together.
Cases of abuse and abandonment of senior citizens have been on the rise in Taiwan in recent years, prompting lawmakers to propose a bill to jail adults who fail to look after their elderly parents.
People aged 65 and over account for 10.7 percent of Taiwan's population of 23 million, the latest census showed, above the 7.0 percent level at which a society is defined as "ageing" by the World Health Organisation.