He was riding along a highway, south-east of Toowoomba, when he collided with a truck.
The Toowoomba RACQ LifeFlight Rescue team was tasked to the scene, shortly before 2:30 this afternoon.
The man was treated for multiple injuries, before being loaded into the helicopter.
While en route to hospital, his condition deteriorated.
The aeromedical team landed at Toowoomba Hospital to stabilise him, before he was airlifted to the PA Hospital in a serious, but stable condition.