Third-party punishment has been regarded as an important mechanism to promote fairness. Although previous research has shown that children aged 6 and older punish unfair behaviors at a personal cost, it is unknown whether they actually intend to establish equality or whether equality is a mere byproduct of punishment. In this preregistered study, N = 60 five- to 9-year-olds witnessed that an agent made unfair resource allocations to a peer. Children could then decide not only whether to punish but also how much to punish. We found that with age, children's intervention is more likely to equalize outcomes between third parties (e.g., turning 3:1 into 1:1). In conclusion, the egalitarian motive to reduce differences in payoffs could underlie children's punishment over development.