The present disclosure provides a heat exchanger for a vehicle. The heat exchanger includes a relay block and a base member. The relay block has a first passage and a second passage. The relay block includes a first connecting surface and a second connecting surface. The base member is formed of plastic. The first connecting surface is configured to be connected to a first connector that is in fluid communication with a first in-vehicle component. The second connecting surface is configured to be connected to a second connector that is in fluid communication with a second in-vehicle component. Heat medium flows into the first in-vehicle component through the first passage and the heat medium flows into the second in-vehicle component through the second passage. The relay block is integrally formed with the base member by molding.