A material testing machine comprising: a pair of first moving members capable of moving in mutually approaching and separating directions along a first axis by being guided along a guide member; chucks correspondingly connected to the first moving members; a pair of second moving members capable of moving in mutually approaching and separating directions along a second axis intersecting with the first axis by being guided along a guide member; chucks correspondingly connected to the second moving members; a load member to be applied with a load by a load mechanism; four link members that are disposed in states of being swingable with respect to the load member correspondingly around swing shafts disposed in the load member; and connecting mechanisms adapted to connect end parts of the link members on sides opposite to the swing shafts to the first moving members and the second moving members correspondingly, wherein the material testing machine is adapted to transmit the load applied to the load member to the pair of first moving members and the pair of second moving members through the four link members correspondingly, and is adapted to thereby synchronously move the pair of first moving members in the mutually separating directions along the first axis, as well as to move the pair of second moving members in the mutually separating directions along the second axis, and the material testing machine comprises pretension mechanisms adapted to apply pretensions to a test piece by, in a state where no load is applied to the load member by the load mechanism, moving the pair of chucks correspondingly connected to the pair of first moving member in the mutually separating directions along the first axis as well as moving the pair of chucks correspondingly connected to the pair of second moving members in the mutually separating directions along the second axis, characterized in that the connecting mechanisms include: - pins provided in connect end parts of the link members on sides opposite to the swing shafts; - seat members formed with seating surfaces provided in the first moving members and the second moving members and touching the pins correspondingly; and - slide members (21, 22) correspondingly connected to the chucks and adapted to hold the seat members, wherein the pretension mechanisms have pressing members adapted to move the seat members with respect to the slide members (21, 22) correspondingly, and the pretension mechanisms are adapted to apply the pretensions to the test piece by changing distances between the pins and the chucks correspondingly. a pair of first moving members capable of moving in mutually approaching and separating directions along a first axis by being guided along a guide member; chucks correspondingly connected to the first moving members; a pair of second moving members capable of moving in mutually approaching and separating directions along a second axis intersecting with the first axis by being guided along a guide member; chucks correspondingly connected to the second moving members; a load member to be applied with a load by a load mechanism; four link members that are disposed in states of being swingable with respect to the load member correspondingly around swing shafts disposed in the load member; and connecting mechanisms adapted to connect end parts of the link members on sides opposite to the swing shafts to the first moving members and the second moving members correspondingly, wherein the material testing machine is adapted to transmit the load applied to the load member to the pair of first moving members and the pair of second moving members through the four link members correspondingly, and is adapted to thereby synchronously move the pair of first moving members in the mutually separating directions along the first axis, as well as to move the pair of second moving members in the mutually separating directions along the second axis, and the material testing machine comprises pretension mechanisms adapted to apply pretensions to a test piece by, in a state where no load is applied to the load member by the load mechanism, moving the pair of chucks correspondingly connected to the pair of first moving member in the mutually separating directions along the first axis as well as moving the pair of chucks correspondingly connected to the pair of second moving members in the mutually separating directions along the second axis, characterized in that the connecting mechanisms include: - pins provided in connect end parts of the link members on sides opposite to the swing shafts; - seat members formed with seating surfaces provided in the first moving members and the second moving members and touching the pins correspondingly; and - slide members (21, 22) correspondingly connected to the chucks and adapted to hold the seat members, - pins provided in connect end parts of the link members on sides opposite to the swing shafts; - seat members formed with seating surfaces provided in the first moving members and the second moving members and touching the pins correspondingly; and - slide members (21, 22) correspondingly connected to the chucks and adapted to hold the seat members, wherein the pretension mechanisms have pressing members adapted to move the seat members with respect to the slide members (21, 22) correspondingly, and the pretension mechanisms are adapted to apply the pretensions to the test piece by changing distances between the pins and the chucks correspondingly.