The present invention provides a vehicle body soundproof structure Sp that is configured to block noise from outside a vehicle, and comprises a window panel 24 fixed in a window frame 22 located on a side portion of a vehicle body 10, an interior material 50 provided at a vehicle interior side of the window frame 22 and having an upper end portion 52 extending diagonally upward in a direction toward the window panel 24, and a soundproof member 60 fixed to the upper end portion 52 of the interior material 50. The soundproof member 60 is provided in contact in a compressed state with an inner surface of the window panel 24 so as to fill a gap G formed between the upper end portion 52 of the interior material 50 and the window panel 24.