The present invention provides feedstock compositions for use of the production of an activated carbon for electric double layer capacitor electrodes or the production of needle coke, comprising a first heavy oil with an initial boiling point of 300° C. or higher, an asphalten content of 12 percent by mass or less, a saturate content of 50 percent by mass or more and a sulfur content of 0.3 percent by mass or less, produced as a residue resulting from vacuum-distillation of a petroleum-based oil and a second heavy oil with an initial boiling point of 150° C. or higher and a sulfur content of 0.5 percent by mass or less, produced by subjecting a hydrocarbon oil to fluidized catalytic cracking.