A magnetic detection device for use in a bank note discriminating apparatus is proposed. A magnetic pattern which has been already formed on each bank note by applying the magnetizable printing ink thereon is detected by a magnetic detecting head of the device. The device further includes a conveyer driven at a conveying speed of V.sub.1, and a positioning roller rotated at a circumferential speed of V.sub.2. According to this invention, the speed V.sub.2 is adjusted to be approximately equal to or only slightly higher than the speed V.sub.1. According to another feature of this invention, the detection face of the magnetic head is spaced from the opposing peripheral face of the positioning roller by a gap D which is greater than the thickness T of the bank notes to be handled. By the use of the device of this invention constructed and operated as aforementioned, the magnetic detecting head is prevented from picking up noise signals caused by impulsive force applied thereon by the impinging leading end of the inserted bank note or uneven compression force otherwise applied thereon by the bank note which is bent on or above the magnetic head when the speed V.sub.2 is appreciably different from the speed V.sub.1 to accelerate or decelerate the travelling speed of the bank note just above the magnetic head.