A method of operating a medical diagnostic apparatus that displays a medical image, the method comprising: modifying, by a controller, an operating state of the medical diagnostic apparatus from a first state to a second state based on sequential first user inputs, wherein the first state is determined as an upper node, and the second state is determined as a subnode of the first state; modifying, by the controller, the operating state of the medical diagnostic apparatus from the second state to a third state based on a second user input, wherein the third state is determined as a subnode of the second state; storing, by a storage unit, a history of a plurality of operating states respectively corresponding to the first user inputs and the second user input, based on a tree structure formed of the upper node and the subnode; modifying, by the controller, the operating state of the medical diagnostic apparatus from the third state to a fourth state based on a third user input, wherein the fourth state is determined as a subnode of the third state; modifying, by the controller, the operating state of the medical diagnostic apparatus from the fourth state to a fifth state based on a fourth user input, wherein the fifth state is determined as a subnode of the fourth state; renewing, by the controller, the history such that the fourth state and the fifth state are further included as subnodes of the third state and the fourth state respectively based on the tree structure and storing, by the storage unit, the renewed history with respect to the fourth state and the fifth state; receiving, by a user input unit, a first recovery input to return to a previous operating state included in the history, based on the tree structure; modifying, by the controller, the operating state of the medical diagnostic apparatus from the fifth state to the third state, based on the first recovery input; modifying, by the controller, the operating state of the medical diagnostic apparatus from the third state to a sixth state and from the sixth state to a seventh state based on a fifth user input and a sixth user input, respectively; renewing, by the controller, the history such that the sixth state and the seventh state are further included as a subnode of the third state and sixth state respectively in parallel with the fourth state and the fifth state based on the tree structure; and storing, by the storage unit, the renewed history of the sixth state and the seventh state, wherein the history with respect to the fourth state and the fifth state stored in the storage unit is not removed and is maintained in the storage unit. modifying, by a controller, an operating state of the medical diagnostic apparatus from a first state to a second state based on sequential first user inputs, wherein the first state is determined as an upper node, and the second state is determined as a subnode of the first state; modifying, by the controller, the operating state of the medical diagnostic apparatus from the second state to a third state based on a second user input, wherein the third state is determined as a subnode of the second state; storing, by a storage unit, a history of a plurality of operating states respectively corresponding to the first user inputs and the second user input, based on a tree structure formed of the upper node and the subnode; modifying, by the controller, the operating state of the medical diagnostic apparatus from the third state to a fourth state based on a third user input, wherein the fourth state is determined as a subnode of the third state; modifying, by the controller, the operating state of the medical diagnostic apparatus from the fourth state to a fifth state based on a fourth user input, wherein the fifth state is determined as a subnode of the fourth state; renewing, by the controller, the history such that the fourth state and the fifth state are further included as subnodes of the third state and the fourth state respectively based on the tree structure and storing, by the storage unit, the renewed history with respect to the fourth state and the fifth state; receiving, by a user input unit, a first recovery input to return to a previous operating state included in the history, based on the tree structure; modifying, by the controller, the operating state of the medical diagnostic apparatus from the fifth state to the third state, based on the first recovery input; modifying, by the controller, the operating state of the medical diagnostic apparatus from the third state to a sixth state and from the sixth state to a seventh state based on a fifth user input and a sixth user input, respectively; renewing, by the controller, the history such that the sixth state and the seventh state are further included as a subnode of the third state and sixth state respectively in parallel with the fourth state and the fifth state based on the tree structure; and storing, by the storage unit, the renewed history of the sixth state and the seventh state, wherein the history with respect to the fourth state and the fifth state stored in the storage unit is not removed and is maintained in the storage unit.