An in-vehicle apparatus mounting unit having a projection projecting into a cabin interior includes: a panel provided to face the cabin interior; a support for supporting the projection while the projection is made to project from the panel; and a support case that is attached to the panel on an opposite side to the cabin and accommodates the support in a space formed thereby together with the panel. The support is fixed to the panel or the support case by fixing means, and the fixing means releases the fixation for the support when a load pushing the projection toward the panel exceeds a predetermined load.