A vehicle side portion structure comprising: a vehicle pillar structure; a front pillar to which the vehicle pillar structure is applied; a front side door that opens and closes a front door opening as the door opening having the front pillar disposed on the edge side of the door opening; and a beltline reinforcement that is provided in the front side door and is disposed along a beltline, wherein the vehicle pillar structure comprises: a plurality of pillar frame structure portions (50, 60), the pillar frame structure portions (50, 60) being disposed on an edge side of an upper half of the door opening as a portion of the pillar in a vehicle side portion, being provided in parallel with an interval between the pillar frame structure portions (50, 60) in a direction perpendicular to a longitudinal direction of the pillar as viewed from an inside of a vehicle cabin, being configured as separate members, being formed in a hollow columnar shape, and having upper and lower end portions fixed to a frame member (24, 30) of the vehicle side portion; a transparent member (70, 72) that is formed of a transparent material and is bridged between the pillar frame structure portions (50, 60) that are adjacent to each other; and a connection member (80, 82) that is formed separately from members constituting the pillar frame structure portions (50, 60), the frame member (24, 30), and the transparent member (70, 72), and connects the pillar frame structure portions (50, 60) that are adjacent to each other, the vehicle side portion structure being characterized in that the connection member includes a lower connection member that connects lower portions of the pillar frame structure portions (50, 60) that are adjacent to each other, and the lower connection member includes a load transmission portion that is located on a vehicle front side of the beltline reinforcement in a state in which the front side door is closed and is configured to transmit a load from the vehicle front side to a front end portion side of the beltline reinforcement. a vehicle pillar structure; a front pillar to which the vehicle pillar structure is applied; a front side door that opens and closes a front door opening as the door opening having the front pillar disposed on the edge side of the door opening; and a beltline reinforcement that is provided in the front side door and is disposed along a beltline, wherein the vehicle pillar structure comprises: a plurality of pillar frame structure portions (50, 60), the pillar frame structure portions (50, 60) being disposed on an edge side of an upper half of the door opening as a portion of the pillar in a vehicle side portion, being provided in parallel with an interval between the pillar frame structure portions (50, 60) in a direction perpendicular to a longitudinal direction of the pillar as viewed from an inside of a vehicle cabin, being configured as separate members, being formed in a hollow columnar shape, and having upper and lower end portions fixed to a frame member (24, 30) of the vehicle side portion; a transparent member (70, 72) that is formed of a transparent material and is bridged between the pillar frame structure portions (50, 60) that are adjacent to each other; and a connection member (80, 82) that is formed separately from members constituting the pillar frame structure portions (50, 60), the frame member (24, 30), and the transparent member (70, 72), and connects the pillar frame structure portions (50, 60) that are adjacent to each other, the vehicle side portion structure being characterized in that the connection member includes a lower connection member that connects lower portions of the pillar frame structure portions (50, 60) that are adjacent to each other, and the lower connection member includes a load transmission portion that is located on a vehicle front side of the beltline reinforcement in a state in which the front side door is closed and is configured to transmit a load from the vehicle front side to a front end portion side of the beltline reinforcement. a plurality of pillar frame structure portions (50, 60), the pillar frame structure portions (50, 60) being disposed on an edge side of an upper half of the door opening as a portion of the pillar in a vehicle side portion, being provided in parallel with an interval between the pillar frame structure portions (50, 60) in a direction perpendicular to a longitudinal direction of the pillar as viewed from an inside of a vehicle cabin, being configured as separate members, being formed in a hollow columnar shape, and having upper and lower end portions fixed to a frame member (24, 30) of the vehicle side portion; a transparent member (70, 72) that is formed of a transparent material and is bridged between the pillar frame structure portions (50, 60) that are adjacent to each other; and a connection member (80, 82) that is formed separately from members constituting the pillar frame structure portions (50, 60), the frame member (24, 30), and the transparent member (70, 72), and connects the pillar frame structure portions (50, 60) that are adjacent to each other, the vehicle side portion structure being characterized in that the connection member includes a lower connection member that connects lower portions of the pillar frame structure portions (50, 60) that are adjacent to each other, and the lower connection member includes a load transmission portion that is located on a vehicle front side of the beltline reinforcement in a state in which the front side door is closed and is configured to transmit a load from the vehicle front side to a front end portion side of the beltline reinforcement.