A position sensor comprising: a magnetic recording medium including two incremental layers (12, 13) and an absolute layer, said absolute layer provided between said incremental layers (12, 13), each of said layers (12, 13, 14) having magnetic information recorded therein; and magnetic detection means including a first magnetoresistance effect incremental layer sensor, a second magnetoresistance effect incremental layer sensor and a magnetoresistance effect absolute layer sensor opposite to said layers (12, 13, 14) of said magnetic recording medium, being moved relative to said magnetic recording medium in the extending direction of said layers (12, 13, 14), and being operative to detect said magnetic information in said layers (12, 13, 14) by said magnetoresistance effect sensors (24, 25, 26), wherein said magnetic detection means has bias magnetic field generating means disposed opposite to said layer sensors (24, 25, 26) and operative to generate bias magnetic fields corresponding to said layer sensors (24, 25, 26), characterized in that the bias magnetic field generating means comprises an absolute layer bias magnet member, a first incremental layer bias magnet member and a second incremental layer bias magnet member stacked on the absolute layer bias magnet member, where the first incremental layer bias magnet member is arranged so as to cover only the first incremental layer sensor, the second incremental layer bias magnet member is arranged so as to cover only the second incremental layer sensor and the absolute layer bias magnet member covers the three sensors (24, 25, 26), where the magnetic polarization senses of the incremental layer bias magnet members are opposed to each other, so that the bias magnetic field for the absolute layer sensor interposed therebetween is reduced. a magnetic recording medium including two incremental layers (12, 13) and an absolute layer, said absolute layer provided between said incremental layers (12, 13), each of said layers (12, 13, 14) having magnetic information recorded therein; and magnetic detection means including a first magnetoresistance effect incremental layer sensor, a second magnetoresistance effect incremental layer sensor and a magnetoresistance effect absolute layer sensor opposite to said layers (12, 13, 14) of said magnetic recording medium, being moved relative to said magnetic recording medium in the extending direction of said layers (12, 13, 14), and being operative to detect said magnetic information in said layers (12, 13, 14) by said magnetoresistance effect sensors (24, 25, 26), wherein said magnetic detection means has bias magnetic field generating means disposed opposite to said layer sensors (24, 25, 26) and operative to generate bias magnetic fields corresponding to said layer sensors (24, 25, 26), characterized in that the bias magnetic field generating means comprises an absolute layer bias magnet member, a first incremental layer bias magnet member and a second incremental layer bias magnet member stacked on the absolute layer bias magnet member, where the first incremental layer bias magnet member is arranged so as to cover only the first incremental layer sensor, the second incremental layer bias magnet member is arranged so as to cover only the second incremental layer sensor and the absolute layer bias magnet member covers the three sensors (24, 25, 26),