An automatic analysis device, comprising: a sample disk, a reagent disk, a reaction disk and a plurality of dispensing mechanisms (210, 220) that are disposed on a top face of a main-body casing (400, 615), the sample disk holding a plurality of samples, the reagent disk holding a plurality of types of reagent, the reaction disk holding a plurality of reaction cells, the plurality of dispensing mechanisms each including an arm that rotates and a nozzle fixed to the arm and dispensing the samples and the reagent to the reaction cells held at the reaction disk, and a measurement unit disposed inside the main-body casing, and including a light source that applies light to the reaction cells and a photoreceptor that receives light; characterised in that the measurement unit is a scattered light measurement unit wherein the photoreceptor is arranged to receive scattered light generated from a reaction liquid in the reaction cells irradiated with the light; and the automatic analysis device further comprises: a protective cover (610, 620, 630; 710, 720; 810, 820, 830) that is disposed to cover the top face of the main-body casing, and includes a first protective cover (610; 710; 810) which defines a light-shielding part (617, 618) to block external light and covering at least an area of the reaction disk corresponding to an area above the scattered light measurement unit, a second protective cover (620; 720; 820) to cover the sample disk, and a third protective cover (630; 710, 711; 830) to cover the reagent disk, the second and third protective covers each including a see-through part (621, 631; 711, 721; 820, 830) enabling seeing therethrough to the inside, wherein the first to third protective covers (610, 620, 630; 710, 720; 810, 820, 830) are openable, and the first protective cover is configured not to be openable unless it is opened concurrently with or after the second and third protective covers. a sample disk, a reagent disk, a reaction disk and a plurality of dispensing mechanisms (210, 220) that are disposed on a top face of a main-body casing (400, 615), the sample disk holding a plurality of samples, the reagent disk holding a plurality of types of reagent, the reaction disk holding a plurality of reaction cells, the plurality of dispensing mechanisms each including an arm that rotates and a nozzle fixed to the arm and dispensing the samples and the reagent to the reaction cells held at the reaction disk, and a measurement unit disposed inside the main-body casing, and including a light source that applies light to the reaction cells and a photoreceptor that receives light; characterised in that the measurement unit is a scattered light measurement unit wherein the photoreceptor is arranged to receive scattered light generated from a reaction liquid in the reaction cells irradiated with the light; and the automatic analysis device further comprises: a protective cover (610, 620, 630; 710, 720; 810, 820, 830) that is disposed to cover the top face of the main-body casing, and includes a first protective cover (610; 710; 810) which defines a light-shielding part (617, 618) to block external light and covering at least an area of the reaction disk corresponding to an area above the scattered light measurement unit, a second protective cover (620; 720; 820) to cover the sample disk, and a third protective cover (630; 710, 711; 830) to cover the reagent disk, the second and third protective covers each including a see-through part (621, 631; 711, 721; 820, 830) enabling seeing therethrough to the inside, wherein the first to third protective covers (610, 620, 630; 710, 720; 810, 820, 830) are openable, and the first protective cover is configured not to be openable unless it is opened concurrently with or after the second and third protective covers. a protective cover (610, 620, 630; 710, 720; 810, 820, 830) that is disposed to cover the top face of the main-body casing, and includes a first protective cover (610; 710; 810) which defines a light-shielding part (617, 618) to block external light and covering at least an area of the reaction disk corresponding to an area above the scattered light measurement unit, a second protective cover (620; 720; 820) to cover the sample disk, and a third protective cover (630; 710, 711; 830) to cover the reagent disk, the second and third protective covers each including a see-through part (621, 631; 711, 721; 820, 830) enabling seeing therethrough to the inside, wherein the first to third protective covers (610, 620, 630; 710, 720; 810, 820, 830) are openable, and the first protective cover is configured not to be openable unless it is opened concurrently with or after the second and third protective covers.