This paper proposes a novel ID-based aggregate proxy signature scheme that realizes a warrant-based delegation for an original signer to transfer his/her signing power to a given set of proxy signers. Our proposed scheme allows n distinct proxy signers to sign n distinct messages in such a way that these n individual signatures can be aggregated into a single one without expansion. In the practical applications, such specific kind of aggregate signatures is significantly applausive for enforcing the delegation of authority with both bandwidth and computation savings. Our proposed scheme requires constant bilinear pairing operations for signature verification. Besides, the size of the aggregate proxy signature is the same as that of each of the individual proxy signatures, regardless of the number of participant proxy signers has involved. We also formally sketch the security model of our proposed scheme and show that it is secure against the chosen message attacks under the computational Diffie-Hellman (CDH) assumption.