a mobile display device includes a display part , a speaker , a microphone , an incoming call - detecting part , a state - detecting part , and a display control part . the display part displays information . the speaker outputs voice . the microphone picks up voice . the incoming call - detecting part detects an incoming call . the state - detecting part detects a positional relationship of the speaker and the microphone . the display control part displays , on the display part , information suggesting the correction of the inclination of the apparatus itself , when the incoming call - detecting part detects an incoming call and the state - detecting part detects that the positional relationship of the speaker and the microphone is in a prescribed positional relationship .