In this study, a lab automation system that can fully automate the sample preparation process to be used for liquid chromatography/mass spectrometry (LC/MS) was developed from a modification of a 3D printer. The lab automation system was designed to perform a series of well-organized sample pretreatment steps such as micro pipetting, gripping, vortexing, centrifugation, and heating block shaking without human intervention. The total system consists of three subsystems: an automated liquid handling system (ALHS), which automates the sample preparation process; an automated storage and retrieval system (ASRS), which stores and takes out samples, laboratory consumables, and modularized experimental instruments; and an automated transport system (ATS), which transports objects between ALHS and ASRS. Each subsystem was designed in a modular format to combine the subsystems to create an optimized system for users. All the information needed for the fabrication, including design files, assembly manuals, and software, is released to the public as an open source.