This study analyzed domestic patents and utility models related to menstrual underwear for women, focusing on filing trends, applicant types, regions, IPC classifications, technology combinations, and claim contents. The main technological domains were hygiene and absorption (A61F), clothing construction (A41B), and adhesion/lamination (B29C/B32B), while antibacterial (A61L), textile finishing (D06M), and knitting (D04B) technologies played complementary roles in enhancing hygiene and breathability. From the 1970s to the early 2000s, simple garment structures—mainly basic panty forms with added absorbent or waterproof layers—were commonly protected through utility models filed by individuals. Since the mid-2000s, patent filings have increased, featuring multilayer gradient absorption systems, SAP alternatives, and ergonomic designs that integrate multiple functions and advanced materials. Although individuals accounted for the majority of applicants, early technological development was led by global corporations such as Kimberly-Clark and P&G. Utility models focused on practicality, including washability and replaceability, while patents emphasized advanced performance systems. These findings highlight the need for differentiated design strategies that integrate body-fit, durability, eco-friendly materials, and hygiene– absorption–structure functions, along with international comparative research to enhance competitiveness.