To provide a roof support structure of an open roof car, capable of securing an occupant space in a rollover of a vehicle.

This roof support structure of the open roof car has a collapsible roof 2 openably-closably arranged in an upper part of the vehicle 1 and a roll bar 7 forming an inverse U shape and protecting a head part of an occupant by projecting upward in the rollover of the vehicle. A projecting member 9 is arranged on the upper end of the roll bar 7, and a recessed member 10 is arranged on an inner surface of the collapsible roof 2, respectively. When the roll bar 7 projects upward, the upper end of the roll bar 7 and the collapsible roof 2 are joined by fitting the projecting member 9 in the recessed member 10.