The present invention provides a compound represented by the formula (1). The compound represented by the formula (1) is a developing agent superior in both color-developing sensitivity with low energy and image stability [in the following formula, wherein R1 is a hydrogen atom, an alkyl group, an alkenyl group, an aryl group or an aralkyl group, R2 in the number of m are each independently an alkyl group, an alkenyl group, an aryl group, an aralkyl group, an alkoxy group, a halogen atom, a hydroxy group, a cyano group, a nitro group, a carboxy group or an amino group, R3 in the number of n are each independently an alkyl group, an alkenyl group, an aryl group, an aralkyl group, an alkoxy group, a halogen atom, a hydroxy group, a cyano group, a nitro group, a carboxy group or an amino group, and m and n are each independently an integer of 0-4.