Disclosed is a device for increasing reliability of downlink traffic to mobility devices in an RPL environment that can increase reliability of downlink traffic by dual path generation and redundant packet retransmission for the mobile device in an environment where mobility exists. The moving device includes a directed acyclic graph (DAG) rank value acquisition unit for receiving a destination oriented directed acyclic graph information object (DIO) of parent devices to obtain a DAG rank value of each parent device; a parent device selection unit for selecting prefer parents and alternate parents based on a DAG rank of the parent device; and a destination advertisement object (DAO) signal processing unit for transmitting a DAO to a sync device when the prefer parents and the alternate parents are determined.