The invention relates to an STS crane (Ship-to Shore) which comprises a portal frame structure; a boom (3) which has a portion (3a) extending on a ship's side as well as a portion (3b) extending on aquay side; a trolley (4) moving along the boom; a hoisting mechanism which has a rope drum (7) for hoisting ropes (8), whereby the hoisting ropes are routed from the rope drum through boom ends to thetrolley; auxiliary trolleys (9, 10) which move along the boom on both sides of the trolley to support and/or tighten the hoisting ropes; and a folding joint (16) on the boom portion extending on theship's side for folding up the folding por-tion (3c) of the boom extending to the direction of the ship from the folding joint (16); whereby there are auxiliary trolley rails (17)arranged for the auxiliary trol-leys (9, 10), these auxiliary trolley rails being separate from the trolley rails (6); and whereby the drive roping of the auxiliary trolleys is divided into two separate and independent drive ropings (13, 14) which have separate and independent drive mechanisms (11, 12) and which are on different sides of the folding joint (16) on the boom.