A dual slot SIW antenna unit includes a first substrate, a conductive layer, plural unit radiation members, a second substrate, a ground conductive layer, and two first conductor pillars. The plural unit radiation members are disposed in parallel on the conductive layer, and each unit radiation member includes at least a pair of slots that are disposed in parallel. The two first conductive pillars are disposed between two neighboring unit radiation members and electrically connect the feed routing layer and the conductive layer. A dual slot SIW antenna array module is also disclosed. By use of the dual slot structure, more radiation members are allowed to be included in a limited square measure for improving the antenna gain.