The present invention provides a method of cleaning a cover glass having a spacer which is to be incorporated in a solid image pickup device, comprising: a dry cleaning step performed after dry etching; a wipe-off cleaning step performed after the dry cleaning step; a primary wet cleaning step performed after the wipe-off cleaning step; and a secondary wet cleaning step performed after the primary wet cleaning step, wherein the cover glass having a spacer is fabricated by a manufacturing process including the steps of: bonding a spacer substrate to a glass substrate with an adhesive; applying a photoresist to the spacer substrate; exposing and developing the photoresist by use of a photomask and forming an etching mask corresponding to the spacer on the spacer substrate; and forming a spacer on the glass substrate by the dry etching the spacer substrate.