A laminated circuit board device, comprising a first layer, a second layer, and a third layer, wherein the first layer, the second layer, and the third layer are separated by an insulator (11, 12), and the second layer is disposed between the first layer and the third layer, circuit patterns of the first layer, the second layer, and the third layer are formed on different surfaces parallel to each other by a foil-like conductor, the circuit pattern includes a circuit pattern of an electric power system (P1p) for passing a current flowing between a predetermined power source and a predetermined load, and a circuit pattern of a signal system (P1s) through which a current smaller than that of the power system passes, the circuit pattern of the electric power system (P1p) and the circuit pattern of the signal system (P1s) are disposed in the first layer, respectively, the circuit pattern of the signal system (P2s) is disposed in the second layer, and the circuit pattern of the electric power system (P3p) is disposed in the third layer, the circuit pattern is formed such that shapes of a first circuit pattern (P1p) belonging to the electric power system of the first layer and a second circuit pattern (P3p) belonging to the electric power system of the third layer substantially coincide with each other, for a facing portion facing a protection portion of at least a part of the circuit pattern of the signal system (P2s) in the second layer, characterized in that the specification is defined such that a direction of the current (i2a) flowing through the first circuit pattern and a direction of the current (i2b) flowing through the second circuit pattern coincide with each other, wherein for each of the first circuit pattern (P1p) and the second circuit pattern (P3p), a branching portion (32, 42) and a merging portion (34, 44) are formed between one end and the other end through which a current flows, and a shape is defined such that the sum of the pattern widths (LA1, LB1, LC1, LA3, LB3, LC3) of a plurality of current paths formed between the branching portion (32, 42) and the merging portion (34, 44) is the same in the first circuit pattern (P1p) and the second circuit pattern (P3p). a first layer, a second layer, and a third layer, wherein the first layer, the second layer, and the third layer are separated by an insulator (11, 12), and the second layer is disposed between the first layer and the third layer, circuit patterns of the first layer, the second layer, and the third layer are formed on different surfaces parallel to each other by a foil-like conductor, the circuit pattern includes a circuit pattern of an electric power system (P1p) for passing a current flowing between a predetermined power source and a predetermined load, and a circuit pattern of a signal system (P1s) through which a current smaller than that of the power system passes, the circuit pattern of the electric power system (P1p) and the circuit pattern of the signal system (P1s) are disposed in the first layer, respectively, the circuit pattern of the signal system (P2s) is disposed in the second layer, and the circuit pattern of the electric power system (P3p) is disposed in the third layer, the circuit pattern is formed such that shapes of a first circuit pattern (P1p) belonging to the electric power system of the first layer and a second circuit pattern (P3p) belonging to the electric power system of the third layer substantially coincide with each other, for a facing portion facing a protection portion of at least a part of the circuit pattern of the signal system (P2s) in the second layer, characterized in that the specification is defined such that a direction of the current (i2a) flowing through the first circuit pattern and a direction of the current (i2b) flowing through the second circuit pattern coincide with each other, wherein for each of the first circuit pattern (P1p) and the second circuit pattern (P3p), a branching portion (32, 42) and a merging portion (34, 44) are formed between one end and the other end through which a current flows, and a shape is defined such that the sum of the pattern widths (LA1, LB1, LC1, LA3, LB3, LC3) of a plurality of current paths formed between the branching portion (32, 42) and the merging portion (34, 44) is the same in the first circuit pattern (P1p) and the second circuit pattern (P3p).