A bicycle carrier comprising: a bar having a hitch connector formed to a first end thereof, a connection unit formed to a second end of the bar, two engaging plates extending from the bar and located close to the hitch connector, each engaging plate having a notch, a pin connected between the two engaging plates, the connection unit having a hole; a main tube having a section pivotably connected to the connection unit of the bar by extending a pivot through the hole of the connection unit and the main tube, the main tube having an end cap connected to a first end thereof, a rod extending through the main tube axially, a spring having a first end thereof connected to an inside of the end cap and a second end thereof connected to a first end of the rod by a latch, the latch transversely extending through the main tube, through the first end of the rod and the second end of the spring, the latch removably engaged with the notches of the two engaging plates, an operation member connected to a second end of the main tube, a second end of the rod connected to the operation member so that when the rod is pulled toward the operation member, the latch is dis-engaged from the notches of the two engaging plates, a restriction member pivotably connected to the main tube and removably engaged with the operation member, the restriction member being designed to restrict a movement of the operation member when engaged with the operation member, the main tube being pivotable between a first position and a second position, the main tube at the second position being tilt relative to the bar; a seat connected to the main tube and having two positioning plates, a mount plate attached to the seat and having two passages, the passages each receiving a securing member which secures a front-wheel support and a rear-wheel support, the front-wheel support and the rear-wheel support being respectively and pivotably connected between the two positioning plates of the seat, and a post unit extending from the main tube and having a post and a clamp unit, the clamp unit including a movable part movably connected to the post and a clamp. wherein, when the restriction member is separated from the operation member, the rod can be pulled by pulling the operation member so as to remove the latch from the notches, the main tube is pivoted about the pivot and the hole to pivot the main tube with the seat, the front-wheel support, the rear-wheel support and the post unit from the first position to the second position. a bar having a hitch connector formed to a first end thereof, a connection unit formed to a second end of the bar, two engaging plates extending from the bar and located close to the hitch connector, each engaging plate having a notch, a pin connected between the two engaging plates, the connection unit having a hole; a main tube having a section pivotably connected to the connection unit of the bar by extending a pivot through the hole of the connection unit and the main tube, the main tube having an end cap connected to a first end thereof, a rod extending through the main tube axially, a spring having a first end thereof connected to an inside of the end cap and a second end thereof connected to a first end of the rod by a latch, the latch transversely extending through the main tube, through the first end of the rod and the second end of the spring, the latch removably engaged with the notches of the two engaging plates, an operation member connected to a second end of the main tube, a second end of the rod connected to the operation member so that when the rod is pulled toward the operation member, the latch is dis-engaged from the notches of the two engaging plates, a restriction member pivotably connected to the main tube and removably engaged with the operation member, the restriction member being designed to restrict a movement of the operation member when engaged with the operation member, the main tube being pivotable between a first position and a second position, the main tube at the second position being tilt relative to the bar; a seat connected to the main tube and having two positioning plates, a mount plate attached to the seat and having two passages, the passages each receiving a securing member which secures a front-wheel support and a rear-wheel support, the front-wheel support and the rear-wheel support being respectively and pivotably connected between the two positioning plates of the seat, and a post unit extending from the main tube and having a post and a clamp unit, the clamp unit including a movable part movably connected to the post and a clamp. wherein, when the restriction member is separated from the operation member, the rod can be pulled by pulling the operation member so as to remove the latch from the notches, the main tube is pivoted about the pivot and the hole to pivot the main tube with the seat, the front-wheel support, the rear-wheel support and the post unit from the first position to the second position.