A developing device includes a developer carrying member for carrying a developer to develop an electrostatic image formed on an image bearing member with a developer, wherein an oscillating electric field is formed between the developer carrying member and the image bearing member; a jumping developer blocking member, provided between the image bearing member and the developer carrying member, for blocking a part of a region in which the developer jumps from the developer carrying member to the image bearing member, the jumping developer blocking member including an insulative portion and an electrically floating electroconductive portion opposed to the developer carrying member.