A plant cultivation device comprising: a plurality of fluid passage members formed with a fluid passage through which a culture fluid flows and formed with a through-hole (41a,41b,41c) on an upper surface thereof; a transfer mechanism (13,14,15) which transfers the plurality of fluid passage members such that a distance between two neighboring fluid passage members among the plurality of fluid passage members becomes variable; a seedling culture medium (44a,44b,44c), on which seeds of a plant are arranged; a culture medium holding portion formed in a cylindrical shape, accommodating therein the seedling culture medium (44a,44b,44c) to hold thereof, inserted into the through-hole (41a,41b,41c) of the plurality of the fluid passage members or arranged in communication with the through-hole (41a,41b,41c) of the plurality of fluid passage members and absorbing the culture fluid into the seedling culture medium (44a,44b,44c), characterised in that the plant cultivation device further comprises: a first plate portion (52,152) provided on an upper side of the fluid passage members and formed in a plate shape extending in a transfer direction from the fluid passage members; and a second plate portion (53,153) provided on the upper side of the fluid passage members and formed in a plate shape extending in a direction opposite to the transfer direction from the fluid passage members, wherein when the distance between the two neighboring fluid passage members becomes small, the second plate portion (53,153) provided on a preceding fluid passage member and the first plate portion (52,152) provided on a following fluid passage member are overlapped in an up/down direction; and when the distance between the two neighboring fluid passage members becomes large, the second plate portion (53,153) provided on the preceding fluid passage member and the first plate portion (52,152) provided on the following fluid passage member are separated from each other with respect to the transfer direction. a plurality of fluid passage members formed with a fluid passage through which a culture fluid flows and formed with a through-hole (41a,41b,41c) on an upper surface thereof; a transfer mechanism (13,14,15) which transfers the plurality of fluid passage members such that a distance between two neighboring fluid passage members among the plurality of fluid passage members becomes variable; a seedling culture medium (44a,44b,44c), on which seeds of a plant are arranged; a culture medium holding portion formed in a cylindrical shape, accommodating therein the seedling culture medium (44a,44b,44c) to hold thereof, inserted into the through-hole (41a,41b,41c) of the plurality of the fluid passage members or arranged in communication with the through-hole (41a,41b,41c) of the plurality of fluid passage members and absorbing the culture fluid into the seedling culture medium (44a,44b,44c), characterised in that the plant cultivation device further comprises: a first plate portion (52,152) provided on an upper side of the fluid passage members and formed in a plate shape extending in a transfer direction from the fluid passage members; and a second plate portion (53,153) provided on the upper side of the fluid passage members and formed in a plate shape extending in a direction opposite to the transfer direction from the fluid passage members, wherein when the distance between the two neighboring fluid passage members becomes small, the second plate portion (53,153) provided on a preceding fluid passage member and the first plate portion (52,152) provided on a following fluid passage member are overlapped in an up/down direction; and when the distance between the two neighboring fluid passage members becomes large, the second plate portion (53,153) provided on the preceding fluid passage member and the first plate portion (52,152) provided on the following fluid passage member are separated from each other with respect to the transfer direction. a first plate portion (52,152) provided on an upper side of the fluid passage members and formed in a plate shape extending in a transfer direction from the fluid passage members; and a second plate portion (53,153) provided on the upper side of the fluid passage members and formed in a plate shape extending in a direction opposite to the transfer direction from the fluid passage members, wherein when the distance between the two neighboring fluid passage members becomes small, the second plate portion (53,153) provided on a preceding fluid passage member and the first plate portion (52,152) provided on a following fluid passage member are overlapped in an up/down direction; and when the distance between the two neighboring fluid passage members becomes large, the second plate portion (53,153) provided on the preceding fluid passage member and the first plate portion (52,152) provided on the following fluid passage member are separated from each other with respect to the transfer direction.