A porous copper body, comprising: a skeleton having a three-dimensional network structure, wherein an oxidation-reduction layer formed by an oxidation step followed by a reduction step is provided on the surface of the skeleton, an average crystal grain size D c of the entirety including the skeleton and the oxidation-reduction layer is 5% or more of a diameter R of the copper fibers, the skeleton is constituted by a sintered body made of a plurality of copper fibers, in each of the copper fibers, the diameter R of the copper fibers is set to be in a range of 0.05 mm to 1.0 mm, and a ratio L/R of a length L to the diameter R is set to be in a range of 4 to 2500, the average crystal grain size D c is measured using an EBSD device and the average crystal grain size D c is calculated using the following expression, in which let S be an area of all material except the pores, and let s1, s2, s3,... be areas of each of the crystal grains, and let d 1, d 2, d 3,... be a grain size of each of the crystal grains, D c = d 1 × s 1 / S + d 2 × s 2 / S + d 3 × s 3 / S +.... and the diameter R of the copper fibers is an average value of an equivalent circle diameter (Heywood diameter) R=(A/π) 0.5 ×2, which is calculated through image analysis on a basis of JIS Z 8827-1 using a particle analyzer "Morphologi G3" manufactured by Malvern Instruments Ltd.. a skeleton having a three-dimensional network structure, wherein an oxidation-reduction layer formed by an oxidation step followed by a reduction step is provided on the surface of the skeleton, an average crystal grain size D c of the entirety including the skeleton and the oxidation-reduction layer is 5% or more of a diameter R of the copper fibers, the skeleton is constituted by a sintered body made of a plurality of copper fibers, in each of the copper fibers, the diameter R of the copper fibers is set to be in a range of 0.05 mm to 1.0 mm, and a ratio L/R of a length L to the diameter R is set to be in a range of 4 to 2500, the average crystal grain size D c is measured using an EBSD device and the average crystal grain size D c is calculated using the following expression, in which let S be an area of all material except the pores, and let s1, s2, s3,... be areas of each of the crystal grains, and let d 1, d 2, d 3,... be a grain size of each of the crystal grains, D c = d 1 × s 1 / S + d 2 × s 2 / S + d 3 × s 3 / S +.... and the diameter R of the copper fibers is an average value of an equivalent circle diameter (Heywood diameter) R=(A/π) 0.5 ×2, which is calculated through image analysis on a basis of JIS Z 8827-1 using a particle analyzer "Morphologi G3" manufactured by Malvern Instruments Ltd.. in each of the copper fibers, the diameter R of the copper fibers is set to be in a range of 0.05 mm to 1.0 mm, and a ratio L/R of a length L to the diameter R is set to be in a range of 4 to 2500, the average crystal grain size D c is measured using an EBSD device and the average crystal grain size D c is calculated using the following expression, in which let S be an area of all material except the pores, and let s1, s2, s3,... be areas of each of the crystal grains, and let d 1, d 2, d 3,... be a grain size of each of the crystal grains, D c = d 1 × s 1 / S + d 2 × s 2 / S + d 3 × s 3 / S +.... and the diameter R of the copper fibers is an average value of an equivalent circle diameter (Heywood diameter) R=(A/π) 0.5 ×2, which is calculated through image analysis on a basis of JIS Z 8827-1 using a particle analyzer "Morphologi G3" manufactured by Malvern Instruments Ltd..