A heavy duty pneumatic tire having a nominal aspect ratio of not greater than 65%, the heavy duty pneumatic tire comprising: a tread having at least three circumferential grooves formed thereon; a pair of sidewalls each connected to an end of the tread and located inward of the tread in a radial direction; a pair of beads each located inward of the sidewall in the radial direction; a carcass located inward of the tread and the pair of sidewalls and extending on and between one bead and the other bead; a reinforcing layer located inward of the tread in the radial direction; and a buffer layer located between the carcass and the reinforcing layer in the radial direction, wherein among the at least three circumferential grooves, a circumferential groove located on each outer side in an axial direction is a shoulder circumferential groove, the reinforcing layer includes a belt including a large number of belt cords aligned with each other, and a band including a helically wound band cord, the belt includes a first belt ply, a second belt ply, and a third belt ply, wherein the belt ply located on the innermost side in the radial direction is the first belt ply, and the first belt ply, the second belt ply, and the third belt ply are aligned in the radial direction in this order, a direction in which the belt cords included in the first belt ply are tilted is opposite to a direction in which the belt cords included in the second belt ply are tilted, the band includes a full band located between the first belt ply and the second belt ply in the radial direction, each end of the full band is located outward of the shoulder circumferential groove in the axial direction, the buffer layer is formed from a crosslinked rubber, and a ratio (WB/W1) of a width in the axial direction of the buffer layer to a width in the axial direction of the first belt ply is not less than 50%. a tread having at least three circumferential grooves formed thereon; a pair of sidewalls each connected to an end of the tread and located inward of the tread in a radial direction; a pair of beads each located inward of the sidewall in the radial direction; a carcass located inward of the tread and the pair of sidewalls and extending on and between one bead and the other bead; a reinforcing layer located inward of the tread in the radial direction; and a buffer layer located between the carcass and the reinforcing layer in the radial direction, wherein among the at least three circumferential grooves, a circumferential groove located on each outer side in an axial direction is a shoulder circumferential groove, the reinforcing layer includes a belt including a large number of belt cords aligned with each other, and a band including a helically wound band cord, the belt includes a first belt ply, a second belt ply, and a third belt ply, wherein the belt ply located on the innermost side in the radial direction is the first belt ply, and the first belt ply, the second belt ply, and the third belt ply are aligned in the radial direction in this order, a direction in which the belt cords included in the first belt ply are tilted is opposite to a direction in which the belt cords included in the second belt ply are tilted, the band includes a full band located between the first belt ply and the second belt ply in the radial direction, each end of the full band is located outward of the shoulder circumferential groove in the axial direction, the buffer layer is formed from a crosslinked rubber, and a ratio (WB/W1) of a width in the axial direction of the buffer layer to a width in the axial direction of the first belt ply is not less than 50%.