***Be careful watching this video if you have a weak stomach.***
Justin Bieber must have come down with a real severe case of Bieber Fever last night in Glendale, AZ ... because in the middle of his concert ... he PUKED ON STAGE!!!
The show was the first on his new "Believe" tour and even though he was forced to leave the stage twice due to illness, the show went on.
Bieber apologized to the crowd for being sick, but the crowd didn't seem to mind too much and cheered him on throughout.