A conveyance device comprising: a housing including a first wall portion and a second wall portion facing each other, a first conveyance path provided between the first wall portion and the second wall portion and configured to convey a developer, a second conveyance path provided between the first wall portion and the second wall portion and configured to convey the developer, a separation plate configured to separate the first and second conveyance paths, and a first communication path configured to allow a first end portion of the first conveyance path and a first end portion of the second conveyance path to be in communication with each other via a communication surface, the communication surface including a first region and a second region;, and the first wall portion being perpendicular to a conveyance direction (Da) of the developer in the first conveyance path and a conveyance direction (Db) of the developer in the second conveyance path, characterized in that: the conveyance device further comprising: a formation member configured to form the second region of the communication surface so that a height of the second region from a bottom portion of the first communication path is lower than a height of the first region from the bottom portion of the first communication path; a detection section disposed at the first wall portion on a downstream side of the formation member in the first conveyance path and configured to detect an amount of the developer; and a lid mounted to an upper portion of the housing and configured to cover the first and second conveyance paths, wherein the formation member is provided on the lid, the formation member being a plate-like member disposed downstream of the separation plate in the first conveyance path, successive to the separation plate, and parallel to the separation plate. a housing including a first wall portion and a second wall portion facing each other, a first conveyance path provided between the first wall portion and the second wall portion and configured to convey a developer, a second conveyance path provided between the first wall portion and the second wall portion and configured to convey the developer, a separation plate configured to separate the first and second conveyance paths, and a first communication path configured to allow a first end portion of the first conveyance path and a first end portion of the second conveyance path to be in communication with each other via a communication surface, the communication surface including a first region and a second region;, and the first wall portion being perpendicular to a conveyance direction (Da) of the developer in the first conveyance path and a conveyance direction (Db) of the developer in the second conveyance path, characterized in that: the conveyance device further comprising: a formation member configured to form the second region of the communication surface so that a height of the second region from a bottom portion of the first communication path is lower than a height of the first region from the bottom portion of the first communication path; a detection section disposed at the first wall portion on a downstream side of the formation member in the first conveyance path and configured to detect an amount of the developer; and a lid mounted to an upper portion of the housing and configured to cover the first and second conveyance paths, wherein the formation member is provided on the lid, the formation member being a plate-like member disposed downstream of the separation plate in the first conveyance path, successive to the separation plate, and parallel to the separation plate. a formation member configured to form the second region of the communication surface so that a height of the second region from a bottom portion of the first communication path is lower than a height of the first region from the bottom portion of the first communication path; a detection section disposed at the first wall portion on a downstream side of the formation member in the first conveyance path and configured to detect an amount of the developer; and a lid mounted to an upper portion of the housing and configured to cover the first and second conveyance paths, wherein the formation member is provided on the lid, the formation member being a plate-like member disposed downstream of the separation plate in the first conveyance path, successive to the separation plate, and parallel to the separation plate.