Pain is typically expressed through various sensory (e.g., visual and auditory) modalities: the human voice conveys information about social and affective communication. While the empathic responses to others' pain in the visual modality are modulated by top-down attention constraints, it remains unclear whether empathy for such expressions in the auditory modality also involves such top-down modulation mechanisms. Therefore, the present study investigates how neural correlates of empathic processes to others' vocal pain are modulated by the task-instructed attention manipulations. Each participant completed the following three tasks: (1) Pain Judgment Task, in which participants were instructed to pay attention to pain cues in vocal stimuli, (2) Gender Judgment Task, in which participants were instructed to pay attention to non-pain cues in vocal stimuli; (3) Passive Listening Task, a control task in which participants were instructed to passively listen to the vocal stimuli without any required response. The earlier frontal-central N1 response to either others' painful or neutral voice was greater in the Pain Judgment Task than in the other two tasks, suggesting a general attention modulation on the bottom-up sensory processing of vocal stimuli. The frontal-central P2 responses to others' painful voices was greater in the Pain Judgment Task than in the other two tasks, but not to others' neutral voices, thus suggesting selective attention modulation on the P2 response to others' pain. Late positive complex (LPC) to others' painful and neutral voices differed significantly regardless of task manipulations, thus suggesting empathic pain modulation on LPC response. All these results demonstrated top-down attention modulation on affective sharing responses others' vocal pain, but not on cognitive appraisal process of others' vocal pain.