A developing cartridge includes a receiving member which receives a driving force from outside; a first rotary member which rotates by the driving force; a second rotary member which takes a driven position where the second rotary member rotates by the driving force from the first rotary member and a non-driven position where transmission of the driving force from the first rotary member is cut off; a detectable member which moves as the rotation of the second rotary member, and a first portion which rotates by the driving force. The second rotary member includes a second portion. When the second rotary member is in the non-driven position, the second portion is provided on a rotating locus drawn by the first portion. The first portion engages with the second portion as the first portion rotates, so that the second rotary member rotates from the non-driven position to the driven position.