A stroller apparatus includes a front and a rear leg, a side handrail respectively connected pivotally with the front and rear legs, a handle pivotally connected with the side handrail, a seat support frame including a side bar located below the side handrail and pivotally connected with the front leg and the handle, a first seat detachably installable on the side handrail facing rearward at a first position adjacent to the handle, and a second seat detachably installable on the side bar facing rearward at a second position, the second position being located below the first position and adjacent to the handle.