A heat sink includes first and second fin sets. The first fin set includes a plurality of fins each having a flange extending perpendicularly from an edge thereof and oriented in a same first direction. The flanges engage with each other in succession through locking parts formed thereon. The second fin set includes a plurality of fins each having a flange extending perpendicularly from an edge thereof and oriented in a same second direction toward the first direction. The flanges engage of the second fins with each other in succession through locking parts formed thereon. One of the flanges of an outmost one of the fins of the first fin set and one of the flanges of an outmost one of the fins of the second fin set are extended toward to and engaged with each other.