A waterproof structure having a first case, a second case, a first connector fixed to a mounting hole of the first case, and a second connector fixed to a mounting hole of the second case, the first connector being constructed to be connected to the second connector, the waterproof structure comprising: a ring-shaped first packing provided between a surface of the first case and a surface of the first connector and extending such that the mounting hole of the first case is surrounded thereby, the first packing being constructed to keep waterproof an interface between the first case and the first connector, wherein the surfaces of the first case and the first connector extend orthogonal to a fitting direction of the connectors such that the interface of the first case and the first connector is defined by the surfaces of the first case and the first connector; and a ring-shaped second packing provided between a surface of the second case and an outer circumferential surface of the second connector such that the second packing extends on the outer circumferential surface of the second connector, the second packing being constructed to keep waterproof an interface between the second case and the outer circumferential surface of the second connector, wherein the surface of the second case and the outer circumferential surface of the second connector extend parallel to the fitting direction such that the interface of the second case and the second connector is defined by the surface of the second case and the outer circumferential surface of the second connector, wherein, the first packing is not in contact with the second case or the second connector, and the second packing is not in contact with the first case or the first connector, wherein one of the first connector and the second connector includes a terminal accommodating portion configured to accommodate a terminal and an outer housing fixed to a corresponding one of the first case and the second case, the outer housing being provided in a shape of a cylinder having a bottom and opening toward an other of the first connector and the second connector, characterised in that the outer housing is configured to accommodate therein the terminal accommodating portion movably in the direction orthogonal to the fitting direction; a recess is provided in a shape of a dent on an inner bottom surface of the outer housing and positioning therein the terminal protruding from the terminal accommodating portion; and a ring-shaped fourth packing is provided between the inner bottom surface of the outer housing and the terminal accommodating portion and is adapted to keep waterproof an interface between the inner bottom surface of the outer housing and the terminal accommodating portion, wherein the recess is surrounded by the fourth packing. a ring-shaped first packing provided between a surface of the first case and a surface of the first connector and extending such that the mounting hole of the first case is surrounded thereby, the first packing being constructed to keep waterproof an interface between the first case and the first connector, wherein the surfaces of the first case and the first connector extend orthogonal to a fitting direction of the connectors such that the interface of the first case and the first connector is defined by the surfaces of the first case and the first connector; and a ring-shaped second packing provided between a surface of the second case and an outer circumferential surface of the second connector such that the second packing extends on the outer circumferential surface of the second connector, the second packing being constructed to keep waterproof an interface between the second case and the outer circumferential surface of the second connector, wherein the surface of the second case and the outer circumferential surface of the second connector extend parallel to the fitting direction such that the interface of the second case and the second connector is defined by the surface of the second case and the outer circumferential surface of the second connector, wherein, the first packing is not in contact with the second case or the second connector, and the second packing is not in contact with the first case or the first connector, wherein one of the first connector and the second connector includes a terminal accommodating portion configured to accommodate a terminal and an outer housing fixed to a corresponding one of the first case and the second case, the outer housing being provided in a shape of a cylinder having a bottom and opening toward an other of the first connector and the second connector, characterised in that the outer housing is configured to accommodate therein the terminal accommodating portion movably in the direction orthogonal to the fitting direction; a recess is provided in a shape of a dent on an inner bottom surface of the outer housing and positioning therein the terminal protruding from the terminal accommodating portion; and a ring-shaped fourth packing is provided between the inner bottom surface of the outer housing and the terminal accommodating portion and is adapted to keep waterproof an interface between the inner bottom surface of the outer housing and the terminal accommodating portion, wherein the recess is surrounded by the fourth packing.