We collected aculeate wasps in ten naturally regenerating broad-leaved stands (1–178 years old) and eight Cryptomeria japonica conifer plantations (3–76 years old) using Malaise traps through the wasp flight season (April–November) in Ibaraki Prefecture, Japan. There were 167, 12, and 3605 species, families, and individuals collected, respectively, in the broad-leaved stands and 136, 11, and 2645 in the conifer plantation stands. The most speciose family was Crabronidae, followed by Pompilidae, while in terms of the number of individuals, Pompilidae dominated in every stand. Species richness and abundance were the highest in young stands, decreasing as the stands grew older. Although most collected wasp species preferred young stands, some species characteristically occurred in older stands.