A synchronous folding mechanism is adapted to be mounted to a stroller, and includes a rear joint, a handlebar joint, a front joint, a swing member and a first link member. The handlebar joint and the front joint are rotatably connected to the rear joint. The swing member has opposite end portions, one of which is rotatably connected to the rear joint. The first link member is rotatably connected to the other one of the end portions of the swing member, and is rotatably connected to one of the handlebar joint and the front joint. Rotation of the one of the handlebar joint and the front joint drives a swinging movement of the swing member relative to the rear joint and a movement of the first link member relative to the rear joint.