Disclosed herein is a precombustion chamber structure for a gas engine. The precombustion chamber structure is configured to facilitate disassembly of a precombustion chamber tip, thus making maintenance, repair or inspection of the precombustion chamber easy. For this, the precombustion chamber structure includes: a body (110) having a main body (111), a water jacket (112) and a precombustion chamber tip (113); and a spark plug (120) for igniting fuel gas injected into the precombustion chamber (114) formed in the body (110). The precombustion chamber structure ignites fuel gas and supplies the ignited fuel gas into a main combustion chamber. A tool insert groove (1131) is formed in the junction between the precombustion chamber tip and the water jacket. The tool insert groove (1131) allows a tool for disassembly to be inserted into a space between the precombustion chamber tip and the water jacket.