What literary device is used in the sentence one small step for man giant leap mankind?

The literary device used in the sentence "one small step for man, a giant leap for mankind" is parallelism. Parallelism is the use of a similar grammatical structure in multiple parts of a sentence to create a sense of balance and rhythm. In this case, the parallelism is created by the use of the phrase "one small step" and "a giant leap" in the same sentence.