An image reading apparatus comprising: a reading unit configured to read an image of a document; a feeding unit (43, 44, 44A, 45) configured to feed the document; a carriage configured to hold the reading unit and move the reading unit in a predetermined direction; a motor; a motor-side transmission gear configured to transmit power supplied from the motor; a carriage-side transmission gear configured to transmit the power to the carriage when executing a moving reading of moving the carriage to read the image of the document; a feeding unit-side transmission gear configured to transmit the power to the feeding unit when executing a feeding reading of reading the image of the document that is fed by the feeding unit; a switching gear, the switching gear being a planet gear and configured to: mesh with the feeding unit-side transmission gear at a feeding unit-side position, in which the motor-side transmission gear and the feeding unit-side transmission gear are coupled at a state where the carriage is located at a feeding reading position that is a document reading position, when executing the feeding reading: and mesh with the carriage-side transmission gear at a carriage-side position, in which the motor-side transmission gear and the carriage-side transmission gear are coupled, when executing the moving reading, wherein the switching gear is configured to switch between a meshing state with the carriage-side transmission gear and a meshing state with the feeding unit-side transmission gear; and characterized by a control device configured to perform, when starting to drive the motor for an initialization process of the reading unit: a first switching process (S10 to S35) for meshing the switching gear with the feeding unit-side transmission gear before performing an initialization process of the reading unit; a second switching process for meshing the switching gear with the carriage-side transmission gear after performing the first switching process; and the initialization process of the reading unit after performing the second switching process. a reading unit configured to read an image of a document; a feeding unit (43, 44, 44A, 45) configured to feed the document; a carriage configured to hold the reading unit and move the reading unit in a predetermined direction; a motor; a motor-side transmission gear configured to transmit power supplied from the motor; a carriage-side transmission gear configured to transmit the power to the carriage when executing a moving reading of moving the carriage to read the image of the document; a feeding unit-side transmission gear configured to transmit the power to the feeding unit when executing a feeding reading of reading the image of the document that is fed by the feeding unit; a switching gear, the switching gear being a planet gear and configured to: mesh with the feeding unit-side transmission gear at a feeding unit-side position, in which the motor-side transmission gear and the feeding unit-side transmission gear are coupled at a state where the carriage is located at a feeding reading position that is a document reading position, when executing the feeding reading: and mesh with the carriage-side transmission gear at a carriage-side position, in which the motor-side transmission gear and the carriage-side transmission gear are coupled, when executing the moving reading, wherein the switching gear is configured to switch between a meshing state with the carriage-side transmission gear and a meshing state with the feeding unit-side transmission gear; and characterized by mesh with the feeding unit-side transmission gear at a feeding unit-side position, in which the motor-side transmission gear and the feeding unit-side transmission gear are coupled at a state where the carriage is located at a feeding reading position that is a document reading position, when executing the feeding reading: and mesh with the carriage-side transmission gear at a carriage-side position, in which the motor-side transmission gear and the carriage-side transmission gear are coupled, when executing the moving reading, wherein the switching gear is configured to switch between a meshing state with the carriage-side transmission gear and a meshing state with the feeding unit-side transmission gear; and characterized by a control device configured to perform, when starting to drive the motor for an initialization process of the reading unit: a first switching process (S10 to S35) for meshing the switching gear with the feeding unit-side transmission gear before performing an initialization process of the reading unit; a second switching process for meshing the switching gear with the carriage-side transmission gear after performing the first switching process; and the initialization process of the reading unit after performing the second switching process. a first switching process (S10 to S35) for meshing the switching gear with the feeding unit-side transmission gear before performing an initialization process of the reading unit; a second switching process for meshing the switching gear with the carriage-side transmission gear after performing the first switching process; and the initialization process of the reading unit after performing the second switching process.