An upper part structure of a vehicle body, comprising: a pair of roof side rails (20R, 20L) extending in a longitudinal direction of a vehicle in respective upper left and right lateral portions of the vehicle; a roof panel disposed extending between, and attached to, the pair of roof side rails (20R, 20L) to constitute a roof of the vehicle, the roof panel having a rectangular roof opening; and an opening rear edge reinforcement extending in a lateral direction along a rear edge of the roof opening and attached to the roof panel, the opening rear edge reinforcement having a roof panel opposed surface extending along a lower surface of the roof panel; and a pair of extended reinforcements (30R, 30L) disposed corresponding to respective left and right rear corners of the roof opening so as to extend from the roof panel opposed surface of the opening rear edge reinforcement toward respective left and right lateral end edges of the roof panel as if forming an extension of the roof panel opposed surface, the pair of extended reinforcements being attached to the roof panel near where the roof panel is attached to the roof side rails (20R, 20L), the upper part structure characterized by further comprising a lateral surface outer panel covering an outdoor-side surface of the roof side rail (20R, 20L), wherein the roof side rail (20R, 20L) includes an outer rail member disposed on an outdoor side and an inner rail member disposed on an indoor side, the outer rail member and the inner rail member together defining a closed cross sectional structure, the roof panel is attached to the extended reinforcement (30R, 30L) at first positions (P1, P3) in the longitudinal direction of the vehicle, the lateral surface outer panel, the outer rail member, and the inner rail member are attached to one another at second positions (P2, P4) in the longitudinal direction of the vehicle, and the roof panel, the lateral surface outer panel, and the outer rail member are attached to one another at third positions in the longitudinal direction of the vehicle, the third positions being different from the first positions (P1, P3) and the second positions (P2, P4). a pair of roof side rails (20R, 20L) extending in a longitudinal direction of a vehicle in respective upper left and right lateral portions of the vehicle; a roof panel disposed extending between, and attached to, the pair of roof side rails (20R, 20L) to constitute a roof of the vehicle, the roof panel having a rectangular roof opening; and an opening rear edge reinforcement extending in a lateral direction along a rear edge of the roof opening and attached to the roof panel, the opening rear edge reinforcement having a roof panel opposed surface extending along a lower surface of the roof panel; and a pair of extended reinforcements (30R, 30L) disposed corresponding to respective left and right rear corners of the roof opening so as to extend from the roof panel opposed surface of the opening rear edge reinforcement toward respective left and right lateral end edges of the roof panel as if forming an extension of the roof panel opposed surface, the pair of extended reinforcements being attached to the roof panel near where the roof panel is attached to the roof side rails (20R, 20L), the upper part structure characterized by further comprising a lateral surface outer panel covering an outdoor-side surface of the roof side rail (20R, 20L), wherein the roof side rail (20R, 20L) includes an outer rail member disposed on an outdoor side and an inner rail member disposed on an indoor side, the outer rail member and the inner rail member together defining a closed cross sectional structure, the roof panel is attached to the extended reinforcement (30R, 30L) at first positions (P1, P3) in the longitudinal direction of the vehicle, the lateral surface outer panel, the outer rail member, and the inner rail member are attached to one another at second positions (P2, P4) in the longitudinal direction of the vehicle, and the roof panel, the lateral surface outer panel, and the outer rail member are attached to one another at third positions in the longitudinal direction of the vehicle, the third positions being different from the first positions (P1, P3) and the second positions (P2, P4).