Michigan have reportedly offered Harbaugh a six-year deal worth $48 million, which would make him the highest-paid coach in college football.
Harbaugh's future in San Francisco beyond the season remains uncertain after the 49ers (7-7) were eliminated from play-offs contention last week.
But the 50-year-old, who spent three years playing with Michigan in the 1980s, was tight-lipped about his future plans when quizzed by reporters on Thursday.
"As you know, I only talk about the job that I have," Harbaugh said in his news conference. "Been together a long time. It's a long-standing policy.
"I really don't want to talk about any other job than the one I have or talk about anybody else's process."
Harbaugh added: "I've said that I'm going to finish this to the end.
"I mean... my focus [is] the same as the players' focus, is the same as the coaches' focus - focus on the practice field, the focus in meetings, by the players, by the coaches and by me.
"That is our focus, this football game against the San Diego Chargers and playing well and winning. That's where our energy and focus is."