Ronson Chan Ron-sing, 45, had refused to present his identity card to police during a stop-and-search procedure nearly four years ago.
Deputy Judge Lily Wong Sze-lai dismissed his appeal at the High Court on Friday and ordered him into custody immediately.
Chan was sentenced to five days in jail in 2023 after a magistrate found him guilty of one count of obstructing a police officer and one of obstructing a public officer.
The veteran journalist, who wore a black T-shirt printed with the words “press freedom” to court on Friday, was the association’s chairman from 2021 to 2024.
Some members of the public attending the hearing shouted words of support, telling Chan to take care of himself as he was escorted from the court by Correctional Services Department officers.
Chan’s lawyer said his client would consider taking his case to the Court of Final Appeal.
