Developing apparatus

A developing apparatus includes a developer carrying member for carrying a developer containing magnetic particles; a magnetic member, including first and second magnetic poles which have the same magnetic polarity; a magnetic seal provided opposed to the developer carrying member at a side remote from an image bearing member. The magnetic seal has a third magnetic pole which is most closely opposed to a peak position of the first magnetic pole and which has a magnetic polarity opposite to that of the first magnetic pole, and a fourth magnetic pole which is most closely opposed to a peak position of the second magnetic pole and which has a magnetic polarity opposite to that of the second magnetic pole. Between the third and fourth magnetic poles, the magnetic seal has only one magnetic pole having a polarity opposite to that of the third and fourth magnetic poles.