A portable information terminal device comprising: an imaging unit (104, 105), having a photoelectric conversion element, for photographing an object; imaging unit starting means for executing an initialization process for initializing said photoelectric conversion element by supplying a power source to said imaging unit on the basis of a user's operation; photographing control means for starting photographing operation performed by said imaging unit on the basis of completion of said initialization process; characteristic information storage means for storing characteristic information extracted from face images as registered characteristic information in advance; and authentication processing means for performing an authentication process on the basis of a series of operations, wherein said authentication processing means compares characteristic information extracted from a photographed image with said registered characteristic information to perform said authentication process, said photographed image is photographed by said imaging unit, characterized in that said series of operations is constituted by two or more of user's operations which select one of items displayed in a display part respectively; a last operation within said series of operations is said user's operation which determines switching to a mode needing said authentication process; switching to said mode is carried out on the basis of a result in said authentication process if said last operation is performed, otherwise switching to said mode is not carried out if said last operation is not performed; and said imaging unit starting means starts initializing of said photoelectric conversion element on the basis of said user's operation performed prior to said last operation. an imaging unit (104, 105), having a photoelectric conversion element, for photographing an object; imaging unit starting means for executing an initialization process for initializing said photoelectric conversion element by supplying a power source to said imaging unit on the basis of a user's operation; photographing control means for starting photographing operation performed by said imaging unit on the basis of completion of said initialization process; characteristic information storage means for storing characteristic information extracted from face images as registered characteristic information in advance; and authentication processing means for performing an authentication process on the basis of a series of operations, wherein said authentication processing means compares characteristic information extracted from a photographed image with said registered characteristic information to perform said authentication process, said photographed image is photographed by said imaging unit, characterized in that said series of operations is constituted by two or more of user's operations which select one of items displayed in a display part respectively; a last operation within said series of operations is said user's operation which determines switching to a mode needing said authentication process; switching to said mode is carried out on the basis of a result in said authentication process if said last operation is performed, otherwise switching to said mode is not carried out if said last operation is not performed; and said imaging unit starting means starts initializing of said photoelectric conversion element on the basis of said user's operation performed prior to said last operation. a last operation within said series of operations is said user's operation which determines switching to a mode needing said authentication process; switching to said mode is carried out on the basis of a result in said authentication process if said last operation is performed, otherwise switching to said mode is not carried out if said last operation is not performed; and said imaging unit starting means starts initializing of said photoelectric conversion element on the basis of said user's operation performed prior to said last operation.