A waterproof component includes a housing body, a mat seal, mat seal cover, and an elastic ring. The housing body includes an attachment-hole-insertion portion having a mat-seal-accommodating chamber, an abutting portion to abut a first peripheral surface of the attachment hole, a locking claw provided on an insertion tip side of the attachment hole insertion portion, the locking claw to be locked to a second peripheral surface of the attachment hole, and a cover locking portion provided on an insertion tip side of the attachment-hole-insertion portion. The mat seal has an electric wire press-fitting hole. The mat-seal-accommodating chamber accommodates the mat seal. The mat seal cover locks to the cover-locking portion, the mat seal cover interposes the mat seal between the mat seal cover and a bottom wall of the mat-seal-accommodating chamber. The elastic ring is disposed on an outer periphery of the attachment-hole-insertion portion.