A vehicle lighting device comprising at least a heat sink, a light emitting element, a reflection plate, and a light leakage processing plate, wherein: the heat sink is formed so as to have a flat face (21 H), the light emitting element is mounted in a region of the flat face (21 H) of the heat sink so that light from a light emission surface thereof is emitted in a first direction that crosses the flat face (21 H), the reflection plate is disposed so as to cover the flat face (21 H) of the heat sink, and light from the light emitting element is reflected and then the reflected light is emitted in a second direction that crosses the first direction, the light leakage processing plate is disposed at a peripheral edge part on a side of the first direction of the reflection plate, and is configured so as to scatter light leakage that is not reflected on the reflection plate from among beams of the light from the light emitting element, and is made up of a forward extension portion that is extended over the peripheral edge part of the reflection plate on a side of a forward direction of a vehicle, i.e. a second direction, in a case when the vehicle lighting device is mounted on the vehicle, characterized in that the light leakage processing plate is disposed along the peripheral edge part of the reflection plate so as to have a gap with respect to the peripheral edge part of the reflection plate, and is further made up of a backward extension portion that is extended up to a side of the heat sink over the peripheral edge part of the reflection plate on a side of a backward direction of the vehicle, i.e. in an opposite direction to the second direction, so as to be fixed to the heat sink. the heat sink is formed so as to have a flat face (21 H), the light emitting element is mounted in a region of the flat face (21 H) of the heat sink so that light from a light emission surface thereof is emitted in a first direction that crosses the flat face (21 H), the reflection plate is disposed so as to cover the flat face (21 H) of the heat sink, and light from the light emitting element is reflected and then the reflected light is emitted in a second direction that crosses the first direction, the light leakage processing plate is disposed at a peripheral edge part on a side of the first direction of the reflection plate, and is configured so as to scatter light leakage that is not reflected on the reflection plate from among beams of the light from the light emitting element, and is made up of a forward extension portion that is extended over the peripheral edge part of the reflection plate on a side of a forward direction of a vehicle, i.e. a second direction, in a case when the vehicle lighting device is mounted on the vehicle, characterized in that the light leakage processing plate is disposed along the peripheral edge part of the reflection plate so as to have a gap with respect to the peripheral edge part of the reflection plate, and is further made up of a backward extension portion that is extended up to a side of the heat sink over the peripheral edge part of the reflection plate on a side of a backward direction of the vehicle, i.e. in an opposite direction to the second direction, so as to be fixed to the heat sink.