An image forming apparatus includes: a main body casing; a photosensitive drum; a support member; a belt unit; a transfer roller; and a second sheet guide. The support member is movable between a first accommodated position and a first withdrawn position. The belt unit is movable between a second accommodated position and a second withdrawn position. The belt unit includes: a first sheet guide; and a transfer belt. The belt unit is movable together with the support member. The second sheet guide is positioned below the belt unit and faces the first sheet guide to define a sheet conveying path between the first sheet guide and the second sheet guide in a state where the belt unit is at the second accommodated position. The second sheet guide is configured to convey a sheet along the sheet conveying path toward a position between the transfer belt and the transfer roller.