A display apparatus (100, 200, 300, 400), comprising: a light guide portion (11, 51, 71) that is disposed in front of eyes of a user; a casing (22, 62) that includes a first casing portion (221, 621) and a second casing portion (222, 622) attached to the first casing portion (221, 621) and is fixed to the light guide portion (11, 51, 71), wherein the first casing portion, and the second casing portion (222, 622) are configured to be mutually separable, and wherein the first casing portion (221, 621) constitutes an inner side surface of the casing (22, 62) facing the user, and the second casing portion (222, 622) constitutes an outer side surface of the casing (22, 62); a projection portion (24, 64) that is housed in the casing (22,62) and is capable of projecting an image to the light guide portion (11, 51, 71); a heat source (21, 61) that is disposed within the casing (22, 62) and is supported by the first casing portion (221, 621); and a heat-transfer member (23, 63) that is configured to be deformable and includes a first end (231, 631) and a second end (232, 632), the first end (231, 631) being connected to the heat source (21, 61), the second end (232, 632) being connected to an inner surface of the second casing portion (222, 622), (i) wherein the heat source (21, 61) is a light source, and the projection portion (24, 64) includes a projection optical portion and an image modulation element disposed between the light source and the projection optical portion, or (ii) wherein the heat source (21, 61) is an image display portion including a self-emitting element, and the projection portion (24, 64) includes a projection optical portion that projects a display image of the image display portion to the light guide portion (11, 51, 71). a light guide portion (11, 51, 71) that is disposed in front of eyes of a user; a casing (22, 62) that includes a first casing portion (221, 621) and a second casing portion (222, 622) attached to the first casing portion (221, 621) and is fixed to the light guide portion (11, 51, 71), wherein the first casing portion, and the second casing portion (222, 622) are configured to be mutually separable, and wherein the first casing portion (221, 621) constitutes an inner side surface of the casing (22, 62) facing the user, and the second casing portion (222, 622) constitutes an outer side surface of the casing (22, 62); a projection portion (24, 64) that is housed in the casing (22,62) and is capable of projecting an image to the light guide portion (11, 51, 71); a heat source (21, 61) that is disposed within the casing (22, 62) and is supported by the first casing portion (221, 621); and a heat-transfer member (23, 63) that is configured to be deformable and includes a first end (231, 631) and a second end (232, 632), the first end (231, 631) being connected to the heat source (21, 61), the second end (232, 632) being connected to an inner surface of the second casing portion (222, 622), (i) wherein the heat source (21, 61) is a light source, and the projection portion (24, 64) includes a projection optical portion and an image modulation element disposed between the light source and the projection optical portion, or (ii) wherein the heat source (21, 61) is an image display portion including a self-emitting element, and the projection portion (24, 64) includes a projection optical portion that projects a display image of the image display portion to the light guide portion (11, 51, 71). (i) wherein the heat source (21, 61) is a light source, and the projection portion (24, 64) includes a projection optical portion and an image modulation element disposed between the light source and the projection optical portion, or (ii) wherein the heat source (21, 61) is an image display portion including a self-emitting element, and the projection portion (24, 64) includes a projection optical portion that projects a display image of the image display portion to the light guide portion (11, 51, 71).