A head-up display device configured to be mounted on a helmet, the head-up display device comprising a projection module configured to project display light to a projection target, the display light being used for forming a display image capable of being visually recognized as a virtual image by a user wearing the helmet through the projection target, the projection target being disposed in front of an eye of the user and having both light transmittance and light reflection, wherein the projection module includes a light emitter and a mirror, the light emitter and the mirror being incorporated separately in left and right sides of a chin portion of the helmet, the light emitter being configured to emit display light, the mirror being configured to reflect display light emitted by the light emitter toward the projection target, characterized in that the mirror is disposed in a portion close to one side relative to a center in a left-right direction of the helmet, the light emitter includes a light source (61A, 61B), a first portion, and a second portion, the light emitter being configured to emit light, the first portion forming a first optical path through which light from the light source (61A, 61B) passes, the second portion being connected to a downstream side of the first optical path and forming a second optical path to which light that has passed through the first optical path is introduced, the second portion including a display element configured to generate display light by using light that has passed through the second optical path, the first portion and the second portion are disposed in portions close to another side relative to the center in the left-right direction of the helmet, the first portion is disposed such that the first optical path extends in one of a left-right direction or a top-bottom direction, and the second portion is disposed such that the second optical path extends in another of the left-right direction or the top-bottom direction. a projection module configured to project display light to a projection target, the display light being used for forming a display image capable of being visually recognized as a virtual image by a user wearing the helmet through the projection target, the projection target being disposed in front of an eye of the user and having both light transmittance and light reflection, wherein the projection module includes a light emitter and a mirror, the light emitter and the mirror being incorporated separately in left and right sides of a chin portion of the helmet, the light emitter being configured to emit display light, the mirror being configured to reflect display light emitted by the light emitter toward the projection target, characterized in that the mirror is disposed in a portion close to one side relative to a center in a left-right direction of the helmet, the light emitter includes a light source (61A, 61B), a first portion, and a second portion, the light emitter being configured to emit light, the first portion forming a first optical path through which light from the light source (61A, 61B) passes, the second portion being connected to a downstream side of the first optical path and forming a second optical path to which light that has passed through the first optical path is introduced, the second portion including a display element configured to generate display light by using light that has passed through the second optical path, the first portion and the second portion are disposed in portions close to another side relative to the center in the left-right direction of the helmet, the first portion is disposed such that the first optical path extends in one of a left-right direction or a top-bottom direction, and the second portion is disposed such that the second optical path extends in another of the left-right direction or the top-bottom direction.