A display device for use in a vehicle and configured to perform communication with at least one processor provided in the vehicle, the device comprising: a first display configured to output first light forming first visual information; a second display (820, 1710) spaced apart from the first display so as to form a predetermined angle, wherein the second display (820, 1710) includes a first portion for outputting second light and a second portion for outputting third light; and a light synthesizing unit (830, 1300) configured to transmit the first light, and reflect the second light and the third light generated by different light sources, wherein the light synthesizing unit (830, 1300) comprises: a first light synthesizing portion disposed so that one surface thereof faces a first direction, and configured to transmit the first light therethrough and reflect the second light; and a second light synthesizing portion disposed such that one surface thereof faces a second direction different from the first direction, and configured to transmit the first light therethrough and reflect the third light, wherein a main execution screen, when the main execution screen is output on the second display (820, 1710) in response to an event generation, is divided into first and second sub execution screens on the basis of the first and second portions, and wherein the first sub execution screen is output on the first portion, and the second sub execution screen is output on the second portion in an inverted manner. a first display configured to output first light forming first visual information; a second display (820, 1710) spaced apart from the first display so as to form a predetermined angle, wherein the second display (820, 1710) includes a first portion for outputting second light and a second portion for outputting third light; and a light synthesizing unit (830, 1300) configured to transmit the first light, and reflect the second light and the third light generated by different light sources, wherein the light synthesizing unit (830, 1300) comprises: a first light synthesizing portion disposed so that one surface thereof faces a first direction, and configured to transmit the first light therethrough and reflect the second light; and a second light synthesizing portion disposed such that one surface thereof faces a second direction different from the first direction, and configured to transmit the first light therethrough and reflect the third light, wherein a main execution screen, when the main execution screen is output on the second display (820, 1710) in response to an event generation, is divided into first and second sub execution screens on the basis of the first and second portions, and wherein the first sub execution screen is output on the first portion, and the second sub execution screen is output on the second portion in an inverted manner. a first light synthesizing portion disposed so that one surface thereof faces a first direction, and configured to transmit the first light therethrough and reflect the second light; and a second light synthesizing portion disposed such that one surface thereof faces a second direction different from the first direction, and configured to transmit the first light therethrough and reflect the third light, wherein a main execution screen, when the main execution screen is output on the second display (820, 1710) in response to an event generation, is divided into first and second sub execution screens on the basis of the first and second portions, and wherein the first sub execution screen is output on the first portion, and the second sub execution screen is output on the second portion in an inverted manner.