An image forming apparatus, comprising: a casing provided with an inner space; an opening/closing cover which is mounted on the casing to be openable and closable for opening the inner space to an outside of the image forming apparatus when the opening/closing cover is in an opened state; an exposure device provided with a laser light source which is configured to emit laser light, a housing which is configured to house the laser light source therein and to include an opening for passing the laser light therethrough, and a light transmissive member which is disposed in the housing at such a position as to cover the opening of the housing for transmitting the laser light, the exposure device being disposed in the inner space; an image forming unit provided with an image carrier onto which the laser light transmitted through the light transmissive member is irradiated, the image forming unit being mounted to a first position facing the exposure device in the inner space, and being allowed to be mounted and dismounted to and from the inner space when the opening/closing cover is in the opened state; an airflow generator which is configured to generate an airflow in the inner space; a cooling air path which is configured to guide the airflow between the exposure device and the image forming unit in the inner space; and a partition member (91; 91A; 550) which is disposed between the exposure device and the image forming unit, and is configured to change a state thereof between a first state and a second state, wherein the first state is such that the partition member projects toward the image forming unit mounted to the first position from a side of the exposure device, obstructs an operation of dismounting the image forming unit from the inner space and constitutes part of the cooling air path when the opening/closing cover is in a closed state, the second state is such that the partition member allows the image forming unit to be dismounted from the inner space when the opening/closing cover is in an opened state, and the image forming unit is configured to be shifted to a second position closer to the exposure device than the first position during the dismounting operation of the image forming unit from the inner space. a casing provided with an inner space; an opening/closing cover which is mounted on the casing to be openable and closable for opening the inner space to an outside of the image forming apparatus when the opening/closing cover is in an opened state; an exposure device provided with a laser light source which is configured to emit laser light, a housing which is configured to house the laser light source therein and to include an opening for passing the laser light therethrough, and a light transmissive member which is disposed in the housing at such a position as to cover the opening of the housing for transmitting the laser light, the exposure device being disposed in the inner space; an image forming unit provided with an image carrier onto which the laser light transmitted through the light transmissive member is irradiated, the image forming unit being mounted to a first position facing the exposure device in the inner space, and being allowed to be mounted and dismounted to and from the inner space when the opening/closing cover is in the opened state; an airflow generator which is configured to generate an airflow in the inner space; a cooling air path which is configured to guide the airflow between the exposure device and the image forming unit in the inner space; and a partition member (91; 91A; 550) which is disposed between the exposure device and the image forming unit, and is configured to change a state thereof between a first state and a second state, wherein the first state is such that the partition member projects toward the image forming unit mounted to the first position from a side of the exposure device, obstructs an operation of dismounting the image forming unit from the inner space and constitutes part of the cooling air path when the opening/closing cover is in a closed state, projects toward the image forming unit mounted to the first position from a side of the exposure device, obstructs an operation of dismounting the image forming unit from the inner space and constitutes part of the cooling air path when the opening/closing cover is in a closed state, the second state is such that the partition member allows the image forming unit to be dismounted from the inner space when the opening/closing cover is in an opened state, and the image forming unit is configured to be shifted to a second position closer to the exposure device than the first position during the dismounting operation of the image forming unit from the inner space.