When the user is switched, a driving diagnostic device records the diagnostic result of the user before switched (S180) and starts new diagnosis of the user after switched (S200). Thus, the driving state of each user is individually diagnosed, so that the diagnostic result is suitable. When the travel distance of the vehicle is less than a threshold value (S170: NO, S210: NO), the diagnostic result for such a travel distance is not recorded to exclude the user from the users to which a point or points are given. Hence, the degree of influence on the environment is taken into consideration when the driving is evaluated. Thus, the driving diagnostic device and the driving diagnostic system which diagnose the driving state and evaluate the driving state in accordance with the diagnostic result (giving a point or points) can execute more suitable diagnosis and evaluation.