A fitting structure for a housing constructed from first and second halves. The first half has a fitting projection having a fitting tongue at its forward end. The second half has a pressing section and engagement section for forming a fitting groove. The fitting projection, the pressing section, and the engagement section are formed such that the fitting tongue is placed at a fitting groove's deep end section, along the root of the pressing section. The housing further has a claw projecting inward or outward of the housing and a claw holder engaged with the claw. The claw and the claw holderare placed on either one or the other of a portion of the fitting projection and a portion corresponding to the engagement section. The portion of the fitting projection is located closer to the rootof the fitting projection that the fitting tongue.