An automatic analyzer comprising: a sample vessel transport mechanism for transporting sample vessels; a reagent vessel transport mechanism for transporting reagent vessels; a reaction vessel transport mechanism including a reaction bath and operative to transport a reaction vessel; a sample dispensing mechanism for dispensing a sample in the reaction vessel; a reagent dispensing mechanism for dispensing a reagent in the reaction vessel; a display unit; an operation input portion; a memory; a plurality of analysis modules (ISE, AU1, AU2) each including the sample vessel transport mechanism, the reagent vessel transport mechanism, the reaction vessel transport mechanism, the sample dispensing mechanism, and the reagent dispensing mechanism; and an operation control unit which controls the operations of the analysis modules (ISE, AU1, AU2) and of the display unit, which achieves execution of a plurality of maintenance items by controlling operations of the plurality of analysis modules (ISE, AU1, AU2) according to the order of maintenance items displayed at the display unit, and which conducts an analysis of the sample placed in the reaction vessel, wherein the operation control unit stores, in the memory, an expiration date per maintenance item and execution time per maintenance item of the analysis modules (ISE, AU1, AU2), displays, at the display unit, the execution time along with identification representation of execution priority based on the expiration date, and displays, at the display unit, the individual maintenance items of each of the plurality of analysis modules (ISE, AU1, AU2) with marks permitting the operator to identify whether or not a maintenance item in question can be executed, rearranges the maintenance items in a display order based on the attached marks, and displays the rearranged items at the display unit, wherein the display unit comprises a module display region (302, 601) which displays the maintenance state of each analysis module (ISE, AU1, AU2) on a module basis, and wherein the operation control unit rearranges the display order of the maintenance items based on an operator's selection of one of the names of the plurality of analysis modules (ISE, AU1, AU2) in the module display region (302, 601) in such a manner that the maintenance items which can be executed for the respective analysis module (ISE, AU1, AU2) are displayed at the upper side and based on the execution priority according to an operator's instruction inputted via the operation input portion, and displays the rearranged maintenance items at the display unit. a sample vessel transport mechanism for transporting sample vessels; a reagent vessel transport mechanism for transporting reagent vessels; a reaction vessel transport mechanism including a reaction bath and operative to transport a reaction vessel; a sample dispensing mechanism for dispensing a sample in the reaction vessel; a reagent dispensing mechanism for dispensing a reagent in the reaction vessel; a display unit; an operation input portion; a memory; a plurality of analysis modules (ISE, AU1, AU2) each including the sample vessel transport mechanism, the reagent vessel transport mechanism, the reaction vessel transport mechanism, the sample dispensing mechanism, and the reagent dispensing mechanism; and an operation control unit which controls the operations of the analysis modules (ISE, AU1, AU2) and of the display unit, which achieves execution of a plurality of maintenance items by controlling operations of the plurality of analysis modules (ISE, AU1, AU2) according to the order of maintenance items displayed at the display unit, and which conducts an analysis of the sample placed in the reaction vessel, wherein the operation control unit stores, in the memory, an expiration date per maintenance item and execution time per maintenance item of the analysis modules (ISE, AU1, AU2), displays, at the display unit, the execution time along with identification representation of execution priority based on the expiration date, and displays, at the display unit, the individual maintenance items of each of the plurality of analysis modules (ISE, AU1, AU2) with marks permitting the operator to identify whether or not a maintenance item in question can be executed, rearranges the maintenance items in a display order based on the attached marks, and displays the rearranged items at the display unit, wherein the display unit comprises a module display region (302, 601) which displays the maintenance state of each analysis module (ISE, AU1, AU2) on a module basis, and wherein the operation control unit rearranges the display order of the maintenance items based on an operator's selection of one of the names of the plurality of analysis modules (ISE, AU1, AU2) in the module display region (302, 601) in such a manner that the maintenance items which can be executed for the respective analysis module (ISE, AU1, AU2) are displayed at the upper side and based on the execution priority according to an operator's instruction inputted via the operation input portion, and displays the rearranged maintenance items at the display unit.