A developing roller includes (I) a developing sleeve that is made of nonmagnetic material, and that holds and conveys a developer; and (II) a magnetic member that is fixed inside the developing sleeve, wherein the magnetic member includes (i) a development magnetic pole that corresponds to a development area; (ii) a before-development magnetic pole that is provided at an upstream side of the developer-conveying direction with respect to the development magnetic pole, and that has a polarity different from the development magnetic pole; and (iii) an after-development magnetic pole that is provided at a downstream side of the developer-conveying direction with respect to the development magnetic pole, and that has a polarity different from the development magnetic pole, wherein q1, q2 and q3 satisfy the following formulas q1>90.degree.; and q1+q2>q3, wherein q1, q2 and q3 are defined in the specification.