A panel structure of a sunroof, includes a roof panel for opening and closing an opening of a vehicle roof, an inner panel fixedly attached to a bottom surface of the roof panel along a first outer peripheral portion of the roof panel, an engaging recessed portion provided at the inner panel and curved in a downward direction along the first outer peripheral portion, a second outer peripheral portion provided at the inner panel and positioned below the roof panel while being apart from the roof panel and being directed toward an edge portion of the opening, a weather strip mounted on the first outer peripheral portion, an engaging protruding portion provided at the weather strip, and a seal portion provided at the weather strip and being elastically contactable with the edge portion.