Provided is a labeled precursor compound represented by formula (2). (In the formula, S represents a substrate, L represents a C1-6 linear alkyl group which may contain an ether group, R1 and R2 each independently represent a C1-30 linear or branched alkyl group, or a substituted or unsubstituted monocyclic or fused polycyclic aryl group, each R3 independently represents a C1-4 alkyl group or a C1-4 alkoxy group, and p represents an integer of 0 to 4.)