PROBLEM TO BE SOLVED: To provide a vehicular electric power steering device capable of improving the detection accuracy of a sensor and consistently detecting troubles of the sensor by suppressing any magnetic effect on a magnetostriction type steering torque sensor from the outside. SOLUTION: The vehicular electric power steering device 10 has a rack-and-pinion mechanism 25 consisting of a pinion shaft 24 connected to a steering wheel and a rack shaft 26 connected to steered wheels on a steering system 20 from the steering wheel 21 to the steered wheels 29, detects the steering torque applied to the steering wheel by a magnetostriction type steering torque sensor 41, generates the supporting torque according to the steering torque, and transmits the supporting torque to the pinion shaft. The magnetostriction type steering torque sensor is provided on the pinion shaft. The pinion shaft and the rack shaft are stored in a housing 51. Only a lower portion of the housing is shielded by arranging a magnetic shield 80 formed of a magnetic material to a lower portion below the housing. COPYRIGHT: (C)2006,JPO&NCIPI