An automatic analyzer comprising: a housing which accommodates at least a portion of an analyzer analyzing a specimen to be analyzed; an incubator; an incubator cover which is disposed to cover a preprocessing region provided on an operation surface on the housing so as to include a portion of the analyzer, preprocessing region is a region requiring temperature adjustment and light shielding; and an openable lid which is disposed to openably cover an opening portion, provided in the incubatorcover in order to access the inside from the outside of the preprocessing region, and which is provided to be rotatable between a first fully opened position and a first fully closed position with respect to the incubator cover at an end of the opening portion, the openable lid having an open holding function for holding the openable lid by the first fully opened position in a case where one end of the openable lid on a side distant from the center of rotation of the openable lid is positioned higher than a reference height determined in advance, wherein the incubator cover and the openable lid are provided with heat-insulating properties and light-shielding properties; characterized by further comprising a second region cover which is disposed to cover upper portions of the operation surface including the preprocessing region and the incubator cover, wherein the second region cover is provided to be rotatable between a second fully opened position and a second fully closed position with respect to the housing at an end of the operation surface, wherein the openable lid is moved to the first fully closed position in association with movement of the second region cover from the second fully opened position to the second fully closed position in a case where the openable lid is at the first fully opened position and the second region cover is at the second fully opened position. a housing which accommodates at least a portion of an analyzer analyzing a specimen to be analyzed; an incubator; an incubator cover which is disposed to cover a preprocessing region provided on an operation surface on the housing so as to include a portion of the analyzer, preprocessing region is a region requiring temperature adjustment and light shielding; and an openable lid which is disposed to openably cover an opening portion, provided in the incubatorcover in order to access the inside from the outside of the preprocessing region, and which is provided to be rotatable between a first fully opened position and a first fully closed position with respect to the incubator cover at an end of the opening portion, the openable lid having an open holding function for holding the openable lid by the first fully opened position in a case where one end of the openable lid on a side distant from the center of rotation of the openable lid is positioned higher than a reference height determined in advance, wherein the incubator cover and the openable lid are provided with heat-insulating properties and light-shielding properties; characterized by further comprising a second region cover which is disposed to cover upper portions of the operation surface including the preprocessing region and the incubator cover, wherein the second region cover is provided to be rotatable between a second fully opened position and a second fully closed position with respect to the housing at an end of the operation surface, wherein the openable lid is moved to the first fully closed position in association with movement of the second region cover from the second fully opened position to the second fully closed position in a case where the openable lid is at the first fully opened position and the second region cover is at the second fully opened position.