A strain detector for detecting a strain developed in a shaft applied with a torque comprises strain-sensitive magnetostrictive elements attached to the shaft in two groups in a chevron pattern. A pair of annular detection coils are wound around a bobbin to surround respective one of the groups of magnetostrictive elements. Two annular yokes made of a soft magnetic material of high permeability are disposed around respective coils across radial gaps. A hollow cylindrical shield of non-magnetic material with a high electrical conductivity is disposed around the two yokes across radial gaps. The magnetostrictive elements may be made of a nickel-iron alloy of 45 to 55% Ni-Fe. The yokes may be made of a nickel-iron alloy of about 80% Ni-Fe or alternatively, of a 6.5% Si-Fe steel. The detector may comprise a second magnetic shield disposed around the first shield of non-magnetic material with a high electrical conductivity. The second shield may be made of the same magnetic material as the yokes.
