In an electrically conductive sheath-core conjugate fiber including an electrically conductive layer made of a thermoplastic polymer (A) containing electrically conductive carbon black fine particles which constitutes a sheath component and a protective layer made of a fiber-forming thermoplastic polymer (B) which constitutes a core component, the ratio of the (A) to the total weight of the (A) and the (B) is 10 to 35% by weight, the L1/L0 ratio is 1.04 to 10.0 where L1 represents the length of a boundary between the core component and the sheath component in a cross section of the conjugate fiber and L0 represents the length of the circumference of a circle having an area equal to a cross sectional area of the core component, the fineness, the strength at break and the elongation at break are each adjusted within specified ranges, the shrinkage in hot water at 100° C. is within a specified range, and the fiber surface coverage of the sheath component is 85% or more. This results in provision of an electrically conductive sheath-core conjugate fiber that is excellent in antistatic performance, which is hardly degraded even after long-term wearing, that is maintained for a long time, and that is excellent in durability. A method for producing the electrically conductive sheath-core conjugate fiber and a dust-proof clothing using such a fiber are also provided.