JUSTIN MOORE got quite a scare early Wednesday morning when his tour bus caught fire... while he was in it.  It was around 4:00 A.M. when Justin and his crew woke up to the smoke alarm going off.

Everyone piled out... and then stood around for 30 minutes in the freezing cold until the bus driver got it under control... and then gave them clearance to go back inside.  Believe it or not, he even got it running enough so they could limp back to the hotel.

Justin made his show that night in Royal Oaks, Michigan... and thanks to a replacement bus, he hasn't had to cancel any other dates.