A knocking sensor comprises: a cylindrical body including a cylindrical portion and a supporting flange provided at an outer circumference of a lower end of the cylindrical portion; parts including an insulating member, an electrode plate and an annular piezoelectric element; and a fixing member including a tubular portion which comprises a holding portion protruding from an outer circumference of the tubular portion and is formed to insert into the cylindrical portion from an upper end of the cylindrical portion, the holding portion being elastically deformable to hold the parts, wherein the fixing member is fixed in the cylindrical portion by inserting the tubular portion into the cylindrical portion from the upper end of the cylindrical portion and wherein the parts are clamped and fixed between the supporting flange and the holding portion by holding the parts elastically with the holding portion, while the fixing member is fixed in the cylindrical portion.