In recent years, paraoxybenzoic acid esters (parabens) have been used in pharmaceuticals, cosmetics, and food additives. Parabens have been reported to have a weak estrogenic effect in in vitro test systems, and it is presumed that the longer the alkyl chain of the paraben, the greater its endocrine-disrupting and reproductive function effects. However, the effects of parabens on human health are still unclear. In this study, we evaluated the effects of six parabens (methyl p-hydroxybenzoate [MP], ethyl p-hydroxybenzoate [EP], propyl p-hydroxybenzoate [PP], isopropyl p-hydroxybenzoate [IPP], butyl p-hydroxybenzoate [BP], and isobutyl p-hydroxybenzoate [IBP]) on the reproductive function of the model organism Caenorhabditis elegans. We used 25, 50, and 100 µg/mL solutions of parabens in 0.1% dimethyl sulfoxide (DMSO). Bioassays (growth and maturation effect tests and reproduction effect tests) were performed on L1 larvae of wild-type C. elegans. In the growth effects test, all parabens were observed to have no effect. In the maturation effects test, there was a significant decrease in maturity at each concentration of five of the six parabens, with the exception being MP. In the reproduction effects test, a significant decrease in the number of lifetime offspring was observed at each concentration of five of the six parabens, with the exception being EP. This decrease was remarkable with PP, which has been reported to adversely affect reproductive function in rats. It is necessary to continue to focus on the estrogen-like action of parabens, including PP, and perform genetic analyses, such as RNA sequencing.