Abstract: A ground electrode has a proximal portion fixed to one end of a metallic housing and a distal portion extending toward one end of a center electrode so that an acute angle is formed between a center electrode axis and an axis of the distal portion of the ground electrode. A columnar ground electrode tip is fixed to a ground electrode end surface. The ground electrode tip protrudes from the ground electrode end surface and extends toward the center electrode along an axis crossing with an axis passing the ground electrode end surface. An axis of the center electrode tip is in a cross or skew relationship with an axis of the ground electrode tip.