A wire harness module device for a vehicle, comprising: a module mounting portion configured to be installed upon a metallic vehicle body portion; and a harness module configured to be positioned upon the module mounting portion; wherein: the harness module comprises: a harness module body proper; and a module cover configured to be capable of protecting the harness module body proper, wherein: the module cover comprises a grounding portion; wherein: the harness module body proper comprises: a signal wiring portion, a substrate portion (15, 31, 32) configured such that the signal wiring portion is installed upon the surface of the module mounting portion side of the said substrate portion (15, 31, 32), and a ground portion installed upon a surface of the module cover side of the harness module body proper; wherein: the signal wire portion is sandwiched between the ground portion and the module mounting portion, and the ground portion is configured to be electrically connected to the metallic vehicle body portion. a module mounting portion configured to be installed upon a metallic vehicle body portion; and a harness module configured to be positioned upon the module mounting portion; wherein: the harness module comprises: a harness module body proper; and a module cover configured to be capable of protecting the harness module body proper, the harness module comprises: a harness module body proper; and a module cover configured to be capable of protecting the harness module body proper, a harness module body proper; and a module cover configured to be capable of protecting the harness module body proper, wherein: the module cover comprises a grounding portion; the module cover comprises a grounding portion; wherein: the harness module body proper comprises: a signal wiring portion, a substrate portion (15, 31, 32) configured such that the signal wiring portion is installed upon the surface of the module mounting portion side of the said substrate portion (15, 31, 32), and a ground portion installed upon a surface of the module cover side of the harness module body proper; the harness module body proper comprises: a signal wiring portion, a substrate portion (15, 31, 32) configured such that the signal wiring portion is installed upon the surface of the module mounting portion side of the said substrate portion (15, 31, 32), and a ground portion installed upon a surface of the module cover side of the harness module body proper; a signal wiring portion, a substrate portion (15, 31, 32) configured such that the signal wiring portion is installed upon the surface of the module mounting portion side of the said substrate portion (15, 31, 32), and a ground portion installed upon a surface of the module cover side of the harness module body proper; wherein: the signal wire portion is sandwiched between the ground portion and the module mounting portion, and the ground portion is configured to be electrically connected to the metallic vehicle body portion. the signal wire portion is sandwiched between the ground portion and the module mounting portion, and the ground portion is configured to be electrically connected to the metallic vehicle body portion.