A maintenance device for a construction machine, comprising: an abnormality detection means for detecting abnormality information of an apparatus installed on the construction machine; an abnormality information output means (60, 61) for outputting the abnormality information about the apparatus detected by the abnormality detection means; a storage unit that stores the abnormality information about the apparatus outputted by the abnormality information output means (60, 61); a controller that controls output processing of the abnormality information output means (60, 61) and storing processing of the storage unit; and a maintenance mode setting means (25, 30) for setting a maintenance mode for performing a maintenance work of the apparatus, characterized in that, the maintenance device further comprises: an engine start up lock unit (25, 30) that locks start up of an engine in a state in which the maintenance mode is set; and an unlock unit (25, 30) that unlocks the start up of the engine if an input password is identical with a preset password, when the maintenance mode is not set, the controller executes the output processing and the storing processing of the abnormality information about the apparatus detected by the abnormality detection means, and when the state in which the maintenance mode is set is continued and the start up of the engine is unlocked by the unlock unit (25, 30), the controller does not execute the output processing and the storing processing of the abnormality information about the apparatus detected by the abnormality detection means. an abnormality detection means for detecting abnormality information of an apparatus installed on the construction machine; an abnormality information output means (60, 61) for outputting the abnormality information about the apparatus detected by the abnormality detection means; a storage unit that stores the abnormality information about the apparatus outputted by the abnormality information output means (60, 61); a controller that controls output processing of the abnormality information output means (60, 61) and storing processing of the storage unit; and a maintenance mode setting means (25, 30) for setting a maintenance mode for performing a maintenance work of the apparatus, characterized in that, the maintenance device further comprises: an engine start up lock unit (25, 30) that locks start up of an engine in a state in which the maintenance mode is set; and an unlock unit (25, 30) that unlocks the start up of the engine if an input password is identical with a preset password, an engine start up lock unit (25, 30) that locks start up of an engine in a state in which the maintenance mode is set; and an unlock unit (25, 30) that unlocks the start up of the engine if an input password is identical with a preset password, when the maintenance mode is not set, the controller executes the output processing and the storing processing of the abnormality information about the apparatus detected by the abnormality detection means, and when the state in which the maintenance mode is set is continued and the start up of the engine is unlocked by the unlock unit (25, 30), the controller does not execute the output processing and the storing processing of the abnormality information about the apparatus detected by the abnormality detection means.