The scintillator single crystal of the invention comprises a cerium-activated orthosilicate compound represented by the following formula (1).
Gd2−(a+x+y+z)LnaLuxCeyLmzSiO5 (1)
(In formula (1), Lm represents at least one element selected from among Pr, Tb and Tm, Ln represents at least one element selected from among lanthanoid elements excluding Pr, Tb and Tm, and Sc, and Y, a represents a value of at least 0 and less than 1, x represents a value of greater than 1 and less than 2, y represents a value of greater than 0 and no greater than 0.01, and z represents a value of greater than 0 and no greater than 0.01. The value of a+x+y+z is no greater than 2.)