Spark plug and method for manufacturing spark plug

摘要

A spark plug having a center electrode, an insulator and a metal shell and satisfying conditions (1) to (5) as defined herein. Also disclosed is a method of manufacturing a spark plug including the step of producing an insulator by preparing a raw material powder in such a manner that the particle size distribution ratio (90% volume diameter/10% volume diameter) between particles of 10% volume diameter and particles of 90% volume diameter in the raw material powder is 3.6 to 5.2, and then, press-forming and sintering the prepared raw material powder.