The invention relates to the technical field of cotton planting, and discloses a cotton collecting device. The device includes a cotton hanging taker-in roller, a rotating cylinder, a machine frame, abase and a motor which is installed on the base, the rotating cylinder is located above the base, the rotating cylinder is installed on the machine frame , the rotating cylinder is in rotary connection with the machine frame, a rotating shaft is arranged in the rotating cylinder, the lower portion of the rotating shaft is connected with the motor, and the lower portion of the rotating shaft is fixedly connected with the rotating cylinder; a rotating disk is arranged above the rotating cylinder and is in rotary connection with the machine frame, the upper portion of the rotating shaft is fixedly connected with the rotating disk, the cotton hanging taker-in roller is installed on the lower portion of the rotating disk and is in rotary connection with the rotating disk and located in the rotating cylinder, the rotating disk is fixedly provided with the stepping motor, and the cotton hanging taker-in roller is fixedly connected with the stepping motor; the side wall of the rotating cylinder is provided with a through hole, an outer cylinder fixedly sleeves the rotating cylinder, the outer cylinder and the rotating cylinder form an inner cavity communicated with the through hole, a negative-pressure fan is provided with a guide pipe, one end of the guide pipe is communicated with the negative-pressure fan, and the other end of the guide pipe is communicated with the inner cavity. The cotton collecting effect of the device is good.