[Problem] To provide a manual breast pump which can be disassembled and assembled easily for cleaning purposes, and which can easily change a negative pressure during expression of milk which is generated by an operating section.[Means for Solving] It is provided an accommodating vessel 11 for storing breast milk, a breast pump main body 21, and a manual operating section 61 attached to the breast pump main body and deforming a negative pressure generating member 30 installed on the breast pump main body. The manual operating section 61 has a lever shape, and has an engagement structure 80 which engages with the engaging section 38 on the breast pump main body 21 side. The engagement structure 80 tilts down the extending section erected in the form of a pillar, the extending section being a part of the negative pressure generating member, and is selectively engaged with a plurality of engaging sections provided in the middle of the extending section upon erecting the extending section.