An optical device for a vehicle lamp, comprising a left-hand drive optical element and a right-hand drive optical element, wherein the left-hand drive optical element comprises a left-hand drive light incident part and a left-hand drive transmission part which is arranged in the light emergent end region of the left-hand drive light incident part and extends in the light emergent direction, and the light emergent end of the left-hand drive transmission part is provided with a left-hand drive cut-off part capable of forming a left-hand drive cut-off line, the left-hand drive cut-off part comprises a left-hand drive cut-off part horizontal line section, a left-hand drive cut-off part turning point section and a left-hand drive cut-off part diagonal section; and the right-hand drive optical element comprises a right-hand drive light incident part and a right-hand drive transmission part which is arranged in the light emergent end region of the right-hand drive light incident part and extends in the light emergent direction, and the light emergent end of the right-hand drive transmission part is provided with a right-hand drive cut-off part capable of forming a right-hand drive cut-off line, the right-hand drive cut-off part comprises a right-hand drive cut-off part horizontal line section, a right-hand drive cut-off part turning point section and a right-hand drive cut-off part diagonal section; the left-hand drive light incident part and the right-hand drive light incident part each comprise a light source connection portion and a lampshade, each light source connection portion is a concave arc surface cavity, and each lampshade is a horn-shaped light condensing cup which is gradually enlarged from the end close to the corresponding light source to the end away from the corresponding light source. the left-hand drive optical element comprises a left-hand drive light incident part and a left-hand drive transmission part which is arranged in the light emergent end region of the left-hand drive light incident part and extends in the light emergent direction, and the light emergent end of the left-hand drive transmission part is provided with a left-hand drive cut-off part capable of forming a left-hand drive cut-off line, the left-hand drive cut-off part comprises a left-hand drive cut-off part horizontal line section, a left-hand drive cut-off part turning point section and a left-hand drive cut-off part diagonal section; and the right-hand drive optical element comprises a right-hand drive light incident part and a right-hand drive transmission part which is arranged in the light emergent end region of the right-hand drive light incident part and extends in the light emergent direction, and the light emergent end of the right-hand drive transmission part is provided with a right-hand drive cut-off part capable of forming a right-hand drive cut-off line, the right-hand drive cut-off part comprises a right-hand drive cut-off part horizontal line section, a right-hand drive cut-off part turning point section and a right-hand drive cut-off part diagonal section; the left-hand drive light incident part and the right-hand drive light incident part each comprise a light source connection portion and a lampshade, each light source connection portion is a concave arc surface cavity, and each lampshade is a horn-shaped light condensing cup which is gradually enlarged from the end close to the corresponding light source to the end away from the corresponding light source.