Wang Ching-hsi, an 83-year-old former engineer, is suspected of giving his wife sleeping pills early Sunday and then killing her, the United Daily News and other papers said.
"Why I did this? It's all on my blog," Mr Wang told journalists while being taken away by Taipei police, according to footage shown on local television.
A blog entry dated December 5 which appeared to be Mr Wang's remained available today and detailed in candid terms how Mr Wang's 80-year-old wife, Sun Yuan-ping, had lost the will to live.
The blog entry said that she was suffering from Parkinson's disease and recently had broken her left leg.
"She is miserable," the blog said.
It referred to an agreement the couple had arrived at a decade ago "to die in peace", and quoted Mr Wang as telling his wife that "when the time comes, I will kill you".
After allegedly killing his wife, Mr Wang called the police to turn himself in and waited in his apartment for the officers to arrive, United Daily News said.
Euthanasia and the right to die has been a hotly debated topic in Taiwan in recent years.
In June, the cabinet passed draft regulations allowing terminally ill patients or their relatives to give up medical efforts that prolong suffering without preventing eventual death.
Is it right to die??
What can you see base on the true story above??
In ones opinion, that guy is a murderer.
But in another point of view, can this be an act of mercy to end the suffering??
Life is full of mystery, someone wants to life longer, someone wants to die.
But what if he or she are unable to attempt suicide and call someone else to help.
Will that man be charged for murder case?
Or should the Law add in an exception to killing with reasonable explanation??
What should we do about it?
Laws exist to eliminate chaos. But what if someones wants other to take their life?
What should we do about it?