This book constitutes the refereed proceedings of the 20th International Conference on Asia-Pacific Digital Libraries, ICADL 2018, held in Hamilton, New Zealand, in November 2018. The 20 full, 6 short, and 11 work in progress papers presented in this volume were carefully reviewed and selected from 77 submissions. The papers were organized in topical sections named: topic modeling and semantic analysis; social media, web, and news; heritage and localization; user experience; digital library technology; and use cases and digital librarianship.